CVE-2026-33636

Description

LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. In versions 1.6.36 through 1.6.55, an out-of-bounds read and write exists in libpng's ARM/AArch64 Neon-optimized palette expansion path. When expanding 8-bit paletted rows to RGB or RGBA, the Neon loop processes a final partial chunk without verifying that enough input pixels remain. Because the implementation works backward from the end of the row, the final iteration dereferences pointers before the start of the row buffer (OOB read) and writes expanded pixel data to the same underflowed positions (OOB write). This is reachable via normal decoding of attacker-controlled PNG input if Neon is enabled. Version 1.6.56 fixes the issue.

Read the notes from the security team

Status

Show unmaintained releases

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	Not affected
	14.04 LTS trusty	Not affected
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	Not affected
	16.04 LTS xenial	Not affected
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

introduced in 1.6.36 by the following commit: https://github.com/pnggroup/libpng/commit/7734cda20cf1236aef60f3bbd2267c97bbb40869

Patch details

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

Package	Patch details
libpng1.6	Upstream: aba9f18

Severity score breakdown

CVSS version: CVSS v3.0

Base score 7.6 · High

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	Required
Scope	Unchanged
Confidentiality impact	Low
Integrity impact	Low
Availability impact	High

Scores

Parameter	Value
Base score	7.6 · High
Exploitability score	-
Impact score	-

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

References

Related Ubuntu Security Notices (USN)

USN-8251-1
libpng vulnerabilities
7 May 2026

USN-8639-1
libpng vulnerabilities
17 August 2026