🛡️ CVE-2026-33416 — libpng

🟠 CVSS 7.5 — High ⚠️ Exploit Public CWE-416 NVD
7.5
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. A user must be tricked into taking some action. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

Weakness class

CVE-2026-33416 is classified as CWE-416: Use After Free. Memory is used after being released, so its contents may already belong to something else.

Affected software

CVE-2026-33416 is recorded against 1 package.

  • libpng (from 1.2.1 up to 1.6.56)

Timeline and source

Published on 26 March 2026 and last revised on 17 June 2026. A public exploit is known to exist, which raises the urgency of patching considerably. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
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CVE-2026-33416 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 7.5
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE CWE-416
Public Exploit ⚠️ Yes
Source NVD
Published 2026-03-26
Updated 2026-08-11
Modified 2026-06-17

Affected Packages

Software From version Fixed in
libpng 1.2.1 1.6.56

Similar Threats

Exploit Protection

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