CVE-2025-11680
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedOut-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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceOut-of-bounds write vulnerability in libwebsockets' unfilter_scanline function when compiled with LWS_WITH_UPNG enabled. A crafted PNG with an oversized width value triggers an integer overflow during heap allocation size calculation, resulting in a smaller buffer than required. Subsequent writes in unfilter_scanline then overflow the heap buffer, potentially causing a crash.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- Authentication
- X
- User interaction
- A
- Scope
- X
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Verify libwebsockets versionRun 'libwebsockets-test-server --version' or check the library file version with 'strings libwebsockets.so | grep -i version' or check package managerAffected if Installed version falls within the vulnerable range and has not been patched
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Confirm LWS_WITH_UPNG compile-time option is enabledCheck build configuration files, CMakeLists.txt for 'LWS_WITH_UPNG' set to ON, or inspect binary with 'strings binary | grep -i upng'; also check if the libwebsockets-test-png or png-related test binaries existAffected if LWS_WITH_UPNG is compiled into the binary (the vulnerability only triggers when this option is enabled)
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Identify if PNG rendering is actively usedReview application configuration for PNG decoding/display settings, check for any lws_protocol_plugins loading png-related protocols, or examine runtime logs for PNG initialization messagesAffected if The application uses libwebsockets for PNG rendering or has png-related functionality loaded
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Check for anomalous behavior or crashesReview system crash logs, application error logs, and memory dump files for heap overflow indicators occurring during PNG processingAffected if Crashes or memory corruption events are logged during PNG handling operations
User is affected only if the libwebsockets version is vulnerable, LWS_WITH_UPNG was compiled enabled, and the application actively processes PNG files with the affected code path.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataDisable LWS_WITH_UPNG if PNG rendering is not required, otherwise apply vendor patch which should add proper validation of PNG dimensions before allocation to prevent the integer overflow.
- Consultation2.0 h
- Implementation3.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2025-11680 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-11680 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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