Vulnerability-Lookup

GHSA-8XPQ-CJCF-3WH9

Vulnerability from github – Published: 2026-06-16 19:11 – Updated: 2026-06-16 19:11

Summary

Deno: Permission Bypass via Unicode Normalization Mismatch on macOS (APFS)

Details

Summary

Deno's permission system enforces filesystem and execution restrictions by comparing the requested path against the path supplied to --deny-read, --deny-write, --deny-run, or --deny-ffi. On macOS, that comparison was done at the raw-byte level while the APFS filesystem treats different Unicode spellings of the same name as the same file.

That means a program could reach a denied path by spelling it differently than the deny rule. For example, with --deny-read=/secrets/passwörter.txt, a script could still read the file by opening /secrets/passwo\u0308rter.txt (NFD instead of NFC), or /SECRETS/PASSWÖRTER.txt (different case, since default APFS volumes are case-insensitive). Other forms include ligature characters (ﬁ vs fi, ﬀ vs ff, …) and German ß vs ss.

The denied path and the requested path differed at the byte level, so Deno's permission check passed; the kernel then resolved them to the same inode and served the file anyway. The same flaw affected --deny-write, --deny-run, and --deny-ffi, which share the same path-comparison code.

Am I affected?

You are potentially affected if all of the following are true:

You run Deno on macOS (the issue is specific to APFS path-equivalence rules; Linux and Windows are not affected by this variant).
You rely on --deny-read, --deny-write, --deny-run, or --deny-ffi as a security boundary against less-trusted code — a dependency, plugin, or attacker-controlled input.
The protected path contains characters that have alternate Unicode spellings — most commonly accented characters (é, ñ, ö, …), German ß, or Latin ligatures — or you rely on case-sensitivity on a default APFS volume.

If you only run fully trusted code, or your deny rules cover paths that are pure ASCII with no case-sensitive aliases, you are not exposed to this specific bypass.

Impact

A program running with broad --allow-read (or --allow-write / --allow-run / --allow-ffi) but with --deny-* carve-outs for specific paths could read, write, execute, or load via FFI those denied paths by referring to them through a Unicode- or case-equivalent spelling. The sandbox model on macOS was weaker than the flags suggested.

Workaround

If you cannot upgrade immediately:

Prefer --allow-* allowlists over --deny-* denylists. Allow rules match against the original specifier, so an attacker-supplied alternate spelling will not match a path you didn't explicitly grant.
Do not rely on case-sensitivity of paths on macOS for security boundaries; default APFS volumes are case-insensitive.

Fix

On macOS, Deno now normalizes both the deny-rule path and the requested path to NFC and applies Unicode case folding before comparing them. This matches how APFS resolves paths at the inode level, so byte-different but equivalent spellings are now rejected by the same deny rule.

Severity

5.2 (Medium)


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

Show details on source website

JSON

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.7.13"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "deno"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.7.14"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-49401"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-176",
      "CWE-41"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-16T19:11:52Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nDeno\u0027s permission system enforces filesystem and execution restrictions by\ncomparing the requested path against the path supplied to `--deny-read`,\n`--deny-write`, `--deny-run`, or `--deny-ffi`. On macOS, that comparison was\ndone at the raw-byte level while the APFS filesystem treats different Unicode\nspellings of the same name as the same file.\n\nThat means a program could reach a denied path by spelling it differently than\nthe deny rule. For example, with `--deny-read=/secrets/passw\u00f6rter.txt`, a\nscript could still read the file by opening `/secrets/passwo\\u0308rter.txt`\n(NFD instead of NFC), or `/SECRETS/PASSW\u00d6RTER.txt` (different case, since\ndefault APFS volumes are case-insensitive). Other forms include ligature\ncharacters (`\ufb01` vs `fi`, `\ufb00` vs `ff`, \u2026) and German `\u00df` vs `ss`.\n\nThe denied path and the requested path differed at the byte level, so Deno\u0027s\npermission check passed; the kernel then resolved them to the same inode and\nserved the file anyway. The same flaw affected `--deny-write`, `--deny-run`,\nand `--deny-ffi`, which share the same path-comparison code.\n\n## Am I affected?\n\nYou are potentially affected if **all** of the following are true:\n\n1. You run Deno on **macOS** (the issue is specific to APFS path-equivalence\n   rules; Linux and Windows are not affected by this variant).\n2. You rely on `--deny-read`, `--deny-write`, `--deny-run`, or `--deny-ffi`\n   as a security boundary against less-trusted code \u2014 a dependency, plugin,\n   or attacker-controlled input.\n3. The protected path contains characters that have alternate Unicode\n   spellings \u2014 most commonly accented characters (`\u00e9`, `\u00f1`, `\u00f6`, \u2026), German\n   `\u00df`, or Latin ligatures \u2014 or you rely on case-sensitivity on a default\n   APFS volume.\n\nIf you only run fully trusted code, or your deny rules cover paths that are\npure ASCII with no case-sensitive aliases, you are not exposed to this\nspecific bypass.\n\n## Impact\n\nA program running with broad `--allow-read` (or `--allow-write` /\n`--allow-run` / `--allow-ffi`) but with `--deny-*` carve-outs for specific\npaths could read, write, execute, or load via FFI those denied paths by\nreferring to them through a Unicode- or case-equivalent spelling. The sandbox\nmodel on macOS was weaker than the flags suggested.\n\n## Workaround\n\nIf you cannot upgrade immediately:\n\n- Prefer `--allow-*` allowlists over `--deny-*` denylists. Allow rules match\n   against the original specifier, so an attacker-supplied alternate spelling\n   will not match a path you didn\u0027t explicitly grant.\n- Do not rely on case-sensitivity of paths on macOS for security boundaries;\n   default APFS volumes are case-insensitive.\n\n## Fix\n\nOn macOS, Deno now normalizes both the deny-rule path and the requested path\nto NFC and applies Unicode case folding before comparing them. This matches\nhow APFS resolves paths at the inode level, so byte-different but equivalent\nspellings are now rejected by the same deny rule.",
  "id": "GHSA-8xpq-cjcf-3wh9",
  "modified": "2026-06-16T19:11:52Z",
  "published": "2026-06-16T19:11:52Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/denoland/deno/security/advisories/GHSA-8xpq-cjcf-3wh9"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/denoland/deno"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Deno: Permission Bypass via Unicode Normalization Mismatch on macOS (APFS)"
}

CVE-2026-49401 (GCVE-0-2026-49401)

Vulnerability from cvelistv5 – Published: 2026-06-23 17:22 – Updated: 2026-06-23 17:35

Title

Deno Permission Bypass via Unicode Normalization Mismatch on macOS (APFS)

Summary

Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.7.14, Deno's permission system enforces filesystem and execution restrictions by comparing the requested path against the path supplied to --deny-read, --deny-write, --deny-run, or --deny-ffi. On macOS, that comparison was done at the raw-byte level while the APFS filesystem treats different Unicode spellings of the same name as the same file. That means a program could reach a denied path by spelling it differently than the deny rule. This vulnerability is fixed in 2.7.14.

Severity

7.3 (High)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-41 - Improper Resolution of Path Equivalence
CWE-176 - Improper Handling of Unicode Encoding

Assigner

GitHub_M

References

1 reference

URL	Tags
https://github.com/denoland/deno/security/advisor…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version
denoland	deno	Affected: < 2.7.14

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-49401",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-23T17:35:46.438186Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-23T17:35:51.803Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "deno",
          "vendor": "denoland",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.7.14"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.7.14, Deno\u0027s permission system enforces filesystem and execution restrictions by comparing the requested path against the path supplied to --deny-read, --deny-write, --deny-run, or --deny-ffi. On macOS, that comparison was done at the raw-byte level while the APFS filesystem treats different Unicode spellings of the same name as the same file. That means a program could reach a denied path by spelling it differently than the deny rule. This vulnerability is fixed in 2.7.14."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "LOCAL",
            "availabilityImpact": "NONE",
            "baseScore": 7.3,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "LOW",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-41",
              "description": "CWE-41: Improper Resolution of Path Equivalence",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-176",
              "description": "CWE-176: Improper Handling of Unicode Encoding",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-23T17:22:32.266Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/denoland/deno/security/advisories/GHSA-8xpq-cjcf-3wh9",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/denoland/deno/security/advisories/GHSA-8xpq-cjcf-3wh9"
        }
      ],
      "source": {
        "advisory": "GHSA-8xpq-cjcf-3wh9",
        "discovery": "UNKNOWN"
      },
      "title": "Deno Permission Bypass via Unicode Normalization Mismatch on macOS (APFS)"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-49401",
    "datePublished": "2026-06-23T17:22:32.266Z",
    "dateReserved": "2026-05-29T19:08:01.256Z",
    "dateUpdated": "2026-06-23T17:35:51.803Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Action not permitted

GHSA-8XPQ-CJCF-3WH9

Summary

Am I affected?

Impact

Workaround

Fix

CVE-2026-49401 (GCVE-0-2026-49401)

Tags

Sightings

Nomenclature