LIBPNG: Chunk smuggling in push-mode APNG parser via unconsumed chunk body
CVE-2026-40930

5.4MEDIUM

Key Information:

Vendor

Pnggroup

Status
Libpng
Libpng-apng
Vendor
CVE Published:
4 June 2026

What is CVE-2026-40930?

LIBPNG is a reference library for use in applications that process PNG (Portable Network Graphics) raster image files. In version 1.8.0, three inter-frame chunk discard paths in the push-mode APNG parser clear the chunk-header flag without consuming the chunk body and CRC, allowing attacker-controlled bytes inside an ignored ancillary chunk to be reinterpreted as a fresh chunk header on the next call to png_process_data. Commit faf06924688b62d7c1654b5ceddedbde66ffadb4 fixes the issue.

Affected Version(s)

libpng = 1.8.0

libpng-apng >= 1.6.49, <= 1.6.57

References

https://github.com/pnggroup/libpng/security/advisories/GH...
x_refsource_CONFIRM
https://github.com/pnggroup/libpng/commit/faf06924688b62d...
x_refsource_MISC

CVSS V3.1

Score:
5.4
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.