Bug 2456918 (CVE-2026-34757)

Summary:	CVE-2026-34757 libpng: libpng: Information disclosure and data corruption via use-after-free vulnerability
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	ahughes, caswilli, fferrari, gotiwari, jgrulich, jhorak, kaycoth, khosford, kshier, mtorre, mvyas, pjindal, stcannon, teagle, tfitzsim, tpopela, yguenane
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in libpng, a library used for handling PNG (Portable Network Graphics) image files. This vulnerability arises when an application reuses a pointer, previously obtained from functions like png_get_PLTE, by passing it back to a corresponding setter function within the same image structure. This action causes the setter to access memory that has already been deallocated, leading to a use-after-free condition. A local attacker could potentially exploit this flaw to corrupt image metadata or disclose sensitive information from the application's memory.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-04-09 15:02:41 UTC

LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. From 1.0.9 to before 1.6.57, passing a pointer obtained from png_get_PLTE, png_get_tRNS, or png_get_hIST back into the corresponding setter on the same png_struct/png_info pair causes the setter to read from freed memory and copy its contents into the replacement buffer. The setter frees the internal buffer before copying from the caller-supplied pointer, which now dangles. The freed region may contain stale data (producing silently corrupted chunk metadata) or data from subsequent heap allocations (leaking unrelated heap contents into the chunk struct). This vulnerability is fixed in 1.6.57.

Comment 2 Marco Benatto 2026-04-09 22:21:40 UTC

Upstream commits for this issue:

https://github.com/pnggroup/libpng/commit/398cbe3df03f4e11bb031e07f416dfdde3684e8a
https://github.com/pnggroup/libpng/commit/55d20aaa322c9274491cda82c5cd4f99b48c6bcc