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

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Summary

CVECVE-2026-40930
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-04 16:16:36 UTC
Updated2026-06-04 16:23:52 UTC
DescriptionLIBPNG 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.

Risk And Classification

Primary CVSS: v3.1 5.4 MEDIUM from [email protected]

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

EPSS: 0.000310000 probability, percentile 0.094860000 (date 2026-06-09)

Problem Types: CWE-436 | CWE-436 CWE-436: Interpretation Conflict

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
3.1CNADECLARED5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Pnggroup Libpng affected = 1.8.0 Not specified
CNA Pnggroup Libpng-apng affected >= 1.6.49, <= 1.6.57 Not specified

References

ReferenceSourceLinkTags
www.openwall.com/lists/oss-security/2026/05/15/21 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
github.com/pnggroup/libpng/security/advisories/GHSA-c4v6-gxrq-6g2x [email protected] github.com
github.com/pnggroup/libpng/commit/faf06924688b62d7c1654b5ceddedbde66ffadb4 [email protected] github.com
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