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VulnerabilityPublished

CVE-2025-11680: warmcat libwebsockets · Out-of-bounds Write

Affects warmcat libwebsocketsSource CVE Database V5

0

Not known to be exploited · CVSS 5.9 Medium.

Data as of 26 Oct 2026, 12:54 UTC

CVSS 4.0 base score
5.9Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 33% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Oct 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
warmcat libwebsocketsAffected
  • =4.0
Fixed in–

AI-suggested

  1. Immediately audit all deployments of libwebsockets version 4.0 to identify usage of the LWS_WITH_UPNG flag and HTML display stack.
  2. If possible, disable the LWS_WITH_UPNG flag or avoid using the HTML display stack until a patch is available.
  3. Implement strict input validation and filtering on PNG files processed by libwebsockets to detect and block images with suspiciously large width values.
  4. Employ network-level protections such as web application firewalls (WAFs) to detect and block malicious PNG payloads from untrusted sources.
  5. Monitor vendor announcements and subscribe to security advisories for updates or patches addressing this vulnerability.
  6. Consider isolating or sandboxing applications using libwebsockets to limit the impact of potential crashes or memory corruption.
  7. Conduct penetration testing and fuzzing on affected systems to identify if the vulnerability can be exploited in the specific environment.
  8. Prepare incident response plans to quickly address potential exploitation attempts.
  9. Engage with vendors or open-source maintainers to accelerate patch development and deployment.

Description

Out-of-bounds Write in unfilter_scanline in warmcat libwebsockets allows, when the LWS_WITH_UPNG flag is enabled during compilation and the HTML display stack is used, to write past a heap allocated buffer possibly causing a crash, when the user visits an attacker controlled website that contains a crafted PNG file with a big width value that causes an integer overflow which value is used for determining the size of a heap allocation.

References

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