CVE-2026-33416

Publication date 26 March 2026

Last updated 18 August 2026

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

7.5 · High

Score breakdown

Description

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.

Read the notes from the security team

Status

Package Ubuntu Release Status
libpng 26.04 LTS resolute Not in release
25.10 questing Not in release
24.04 LTS noble Not in release
22.04 LTS jammy Not in release
16.04 LTS xenial
Fixed 1.2.54-1ubuntu1.1+esm3
14.04 LTS trusty
Fixed 1.2.50-1ubuntu2.14.04.3+esm2
libpng1.6 26.04 LTS resolute
Not affected
25.10 questing
Fixed 1.6.50-1ubuntu0.5
24.04 LTS noble
Fixed 1.6.43-5ubuntu0.6
22.04 LTS jammy
Fixed 1.6.37-3ubuntu0.5
20.04 LTS focal
Fixed 1.6.37-2ubuntu0.1~esm3
18.04 LTS bionic
Fixed 1.6.34-1ubuntu0.18.04.2+esm3
16.04 LTS xenial
Fixed 1.6.20-2ubuntu0.1~esm4
chromium-browser 26.04 LTS resolute
Not affected
25.10 questing
Not affected
24.04 LTS noble
Not affected
22.04 LTS jammy
Not affected
firefox 26.04 LTS resolute
Not affected
25.10 questing
Not affected
24.04 LTS noble
Not affected
22.04 LTS jammy
Not affected
thunderbird 26.04 LTS resolute
Not affected
25.10 questing
Not affected
24.04 LTS noble
Not affected
22.04 LTS jammy
Not affected

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Notes

mdeslaur

a regression fix was added to 1.6.58

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
libpng1.6

Severity score breakdown

CVSS version: CVSS v3.0

Base score 7.5 · High

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

References

Related Ubuntu Security Notices (USN)

Other references

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