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

mediumCVSS 5.4CVE-2026-40930

CSIRTS triage

vendor: null product: libpngOther

What: Chunk smuggling in the push-mode APNG parser via an unconsumed chunk body.
Who is affected: Users of libpng.
Urgency: Remediation is medium due to the moderate severity and lack of exploitation reports.
Action: Update to the latest version of libpng.

AI-assisted analysis generated from the source advisory — verify against the original.

⚡ Watch libpng

Get an email when a new libpng advisory drops — max one per day, one-click unsubscribe.

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 5.4
Published: 2026-06-09
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40930

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-409300.20% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 10% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-40930	coverage & exploitation status	NVD · CVE.org

Recent advisories for LIBPNG

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

medium[UPDATE] [medium] libpng: Vulnerability allows Denial of Service and information disclosurecert-bund · 2026-07-10
medium[UPDATE] [medium] libpng: Multiple vulnerabilitiescert-bund · 2026-07-10