ubuntu-cve-2026-33416
Vulnerability from osv_ubuntu
Published
2026-03-26 17:16
Modified
2026-05-08 10:16
Summary
Details

LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. In versions 1.2.1 through 1.6.55, png_set_tRNS and png_set_PLTE each alias a heap-allocated buffer between png_struct and png_info, sharing a single allocation across two structs with independent lifetimes. The trans_alpha aliasing has been present since at least libpng 1.0, and the palette aliasing since at least 1.2.1. Both affect all prior release lines png_set_tRNS sets png_ptr->trans_alpha = info_ptr->trans_alpha (256-byte buffer) and png_set_PLTE sets info_ptr->palette = png_ptr->palette (768-byte buffer). In both cases, calling png_free_data (with PNG_FREE_TRNS or PNG_FREE_PLTE) frees the buffer through info_ptr while the corresponding png_ptr pointer remains dangling. Subsequent row-transform functions dereference and, in some code paths, write to the freed memory. A second call to png_set_tRNS or png_set_PLTE has the same effect, because both functions call png_free_data internally before reallocating the info_ptr buffer. Version 1.6.56 fixes the issue.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libpng12-0",
            "binary_version": "1.2.50-1ubuntu2.14.04.3+esm1"
          },
          {
            "binary_name": "libpng3",
            "binary_version": "1.2.50-1ubuntu2.14.04.3+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:14.04:LTS",
        "name": "libpng",
        "purl": "pkg:deb/ubuntu/libpng@1.2.50-1ubuntu2.14.04.3+esm1?arch=source\u0026distro=esm-infra-legacy/trusty"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.2.49-4ubuntu1",
        "1.2.49-5ubuntu1",
        "1.2.50-1ubuntu1",
        "1.2.50-1ubuntu2",
        "1.2.50-1ubuntu2.14.04.1",
        "1.2.50-1ubuntu2.14.04.2",
        "1.2.50-1ubuntu2.14.04.3",
        "1.2.50-1ubuntu2.14.04.3+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libpng12-0",
            "binary_version": "1.2.54-1ubuntu1.1+esm2"
          },
          {
            "binary_name": "libpng3",
            "binary_version": "1.2.54-1ubuntu1.1+esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "libpng",
        "purl": "pkg:deb/ubuntu/libpng@1.2.54-1ubuntu1.1+esm2?arch=source\u0026distro=esm-infra/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.2.51-0ubuntu3",
        "1.2.54-1",
        "1.2.54-1ubuntu1",
        "1.2.54-1ubuntu1.1",
        "1.2.54-1ubuntu1.1+esm1",
        "1.2.54-1ubuntu1.1+esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libpng16-16",
            "binary_version": "1.6.20-2ubuntu0.1~esm3"
          },
          {
            "binary_name": "libpng16-devtools",
            "binary_version": "1.6.20-2ubuntu0.1~esm3"
          },
          {
            "binary_name": "libpng16-tools",
            "binary_version": "1.6.20-2ubuntu0.1~esm3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "libpng1.6",
        "purl": "pkg:deb/ubuntu/libpng1.6@1.6.20-2ubuntu0.1~esm3?arch=source\u0026distro=esm-apps/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.20-2",
        "1.6.20-2ubuntu0.1~esm1",
        "1.6.20-2ubuntu0.1~esm2",
        "1.6.20-2ubuntu0.1~esm3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libpng-tools",
            "binary_version": "1.6.34-1ubuntu0.18.04.2+esm2"
          },
          {
            "binary_name": "libpng16-16",
            "binary_version": "1.6.34-1ubuntu0.18.04.2+esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "libpng1.6",
        "purl": "pkg:deb/ubuntu/libpng1.6@1.6.34-1ubuntu0.18.04.2+esm2?arch=source\u0026distro=esm-infra/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.34-1",
        "1.6.34-1ubuntu0.18.04.1",
        "1.6.34-1ubuntu0.18.04.2",
        "1.6.34-1ubuntu0.18.04.2+esm1",
        "1.6.34-1ubuntu0.18.04.2+esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libpng-tools",
            "binary_version": "1.6.37-2ubuntu0.1~esm2"
          },
          {
            "binary_name": "libpng16-16",
            "binary_version": "1.6.37-2ubuntu0.1~esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "libpng1.6",
        "purl": "pkg:deb/ubuntu/libpng1.6@1.6.37-2ubuntu0.1~esm2?arch=source\u0026distro=esm-infra/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.37-1",
        "1.6.37-2",
        "1.6.37-2ubuntu0.1~esm1",
        "1.6.37-2ubuntu0.1~esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libpng-tools",
            "binary_version": "1.6.37-3ubuntu0.5"
          },
          {
            "binary_name": "libpng16-16",
            "binary_version": "1.6.37-3ubuntu0.5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "libpng1.6",
        "purl": "pkg:deb/ubuntu/libpng1.6@1.6.37-3ubuntu0.5?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.6.37-3ubuntu0.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.37-3build4",
        "1.6.37-3build5",
        "1.6.37-3ubuntu0.1",
        "1.6.37-3ubuntu0.3",
        "1.6.37-3ubuntu0.4"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libpng-tools",
            "binary_version": "1.6.43-5ubuntu0.6"
          },
          {
            "binary_name": "libpng16-16t64",
            "binary_version": "1.6.43-5ubuntu0.6"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "libpng1.6",
        "purl": "pkg:deb/ubuntu/libpng1.6@1.6.43-5ubuntu0.6?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.6.43-5ubuntu0.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.40-1",
        "1.6.40-2",
        "1.6.40-3",
        "1.6.42-1",
        "1.6.43-1",
        "1.6.43-3",
        "1.6.43-5build1",
        "1.6.43-5ubuntu0.1",
        "1.6.43-5ubuntu0.3",
        "1.6.43-5ubuntu0.4",
        "1.6.43-5ubuntu0.5"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libpng-tools",
            "binary_version": "1.6.50-1ubuntu0.5"
          },
          {
            "binary_name": "libpng16-16t64",
            "binary_version": "1.6.50-1ubuntu0.5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "libpng1.6",
        "purl": "pkg:deb/ubuntu/libpng1.6@1.6.50-1ubuntu0.5?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.6.50-1ubuntu0.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.47-1.1",
        "1.6.48-1",
        "1.6.49-1~exp1",
        "1.6.50-1~exp1",
        "1.6.50-1",
        "1.6.50-1ubuntu0.1",
        "1.6.50-1ubuntu0.3",
        "1.6.50-1ubuntu0.4"
      ]
    }
  ],
  "aliases": [],
  "details": "LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. In versions 1.2.1 through 1.6.55, `png_set_tRNS` and `png_set_PLTE` each alias a heap-allocated buffer between `png_struct` and `png_info`, sharing a single allocation across two structs with independent lifetimes. The `trans_alpha` aliasing has been present since at least libpng 1.0, and the `palette` aliasing since at least 1.2.1. Both affect all prior release lines `png_set_tRNS` sets `png_ptr-\u003etrans_alpha = info_ptr-\u003etrans_alpha` (256-byte buffer) and `png_set_PLTE` sets `info_ptr-\u003epalette = png_ptr-\u003epalette` (768-byte buffer). In both cases, calling `png_free_data` (with `PNG_FREE_TRNS` or `PNG_FREE_PLTE`) frees the buffer through `info_ptr` while the corresponding `png_ptr` pointer remains dangling. Subsequent row-transform functions dereference and, in some code paths, write to the freed memory. A second call to `png_set_tRNS` or `png_set_PLTE` has the same effect, because both functions call `png_free_data` internally before reallocating the `info_ptr` buffer. Version 1.6.56 fixes the issue.",
  "id": "UBUNTU-CVE-2026-33416",
  "modified": "2026-05-08T10:16:56Z",
  "published": "2026-03-26T17:16:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-33416"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-33416"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/pnggroup/libpng/security/advisories/GHSA-m4pc-p4q3-4c7j"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/pnggroup/libpng/pull/824"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-8251-1"
    }
  ],
  "related": [
    "USN-8251-1"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-33416"
  ]
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.