Use After Free Affecting libpng15 package, versions <0:1.5.30-9.el8_10


Severity

Recommended
medium

Based on AlmaLinux security rating.

Threat Intelligence

EPSS
1.05% (60th percentile)

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  • Snyk IDSNYK-ALMALINUX8-LIBPNG15-17372404
  • published18 Jun 2026
  • disclosed23 Jun 2026

Introduced: 18 Jun 2026

CVE-2026-33416  (opens in a new tab)
CWE-416  (opens in a new tab)

How to fix?

Upgrade AlmaLinux:8 libpng15 to version 0:1.5.30-9.el8_10 or higher.
This issue was patched in ALSA-2026:26347.

NVD Description

Note: Versions mentioned in the description apply only to the upstream libpng15 package and not the libpng15 package as distributed by AlmaLinux. See How to fix? for AlmaLinux:8 relevant fixed versions and status.

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-&gt;trans_alpha = info_ptr-&gt;trans_alpha (256-byte buffer) and png_set_PLTE sets info_ptr-&gt;palette = png_ptr-&gt;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.

References

CVSS Base Scores

version 3.1