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Out-of-bounds ReadWeakness · CWE-125

CVE-2025-11679

MEDIUM · 5.9 CVSS v4.0 Published 2025-10-20
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
66/100
Remediation priority · Elevated
Remotely reachable No privileges

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 · unedited
Out-of-bounds Read in lws_upng_emit_next_line in warmcat libwebsockets allows, when the LWS_WITH_UPNG flag is enabled during compilation and the HTML display stack is used, to read 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 height dimension.

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 confidence

An out-of-bounds read vulnerability exists in the lws_upng_emit_next_line function of libwebsockets when the LWS_WITH_UPNG flag is enabled during compilation and the HTML display stack is used. A crafted PNG file with an excessively large height dimension can cause the function to read beyond the boundaries of a heap-allocated buffer, potentially causing a denial-of-service via crash.

MitigationDisable the LWS_WITH_UPNG compilation flag if PNG rendering is not required, or update to a patched version of libwebsockets when available. Avoid browsing untrusted websites when using libwebsockets with PNG display capabilities enabled.

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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify libwebsockets installation and version
    Check for libwebsockets library files (libwebsockets.so, libwebsockets.a) and determine the installed version using package manager (dpkg -l libwebsockets, rpm -qi libwebsockets) or by checking library symlinks and version files in /usr/lib/ or /opt/. Compare the version to any available patched versions from the vendor.
    Affected if The installed version is older than the patched version and LWS_WITH_UPNG was compiled in.
  2. Verify if LWS_WITH_UPNG was enabled at compile time
    Inspect the binary or library for presence of PNG-related symbols (strings binary | grep -i upng, nm -D libwebsockets.so | grep -i upng). If the lws_upng_emit_next_line function symbol exists, the vulnerable code path was compiled. Check build configuration files or Makefiles if available in the deployment.
    Affected if The lws_upng_emit_next_line symbol is present in the linked library, indicating LWS_WITH_UPNG was enabled during compilation.
  3. Confirm HTML display stack is in use
    Review application configuration and code to determine if the HTML display stack or any HTML rendering component of libwebsockets is being used. Check for inclusion of lws-html.h or related HTML headers, and look for HTML-related initialization calls in the application code.
    Affected if The application initializes or uses any HTML display functionality from libwebsockets alongside PNG rendering.
  4. Check for PNG processing of untrusted input
    Audit application logs, network traffic, or file processing paths to determine if libwebsockets is processing PNG files from untrusted sources (user uploads, remote URLs, websocket messages). Review the data flow where PNG files are decoded via libwebsockets.
    Affected if The application processes PNG files from untrusted or external sources through libwebsockets PNG decoding functionality.

A user is affected if libwebsockets is compiled with LWS_WITH_UPNG enabled, the HTML display stack is in use, and the application processes crafted PNG files with large height dimensions, potentially causing an out-of-bounds read crash.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Disable the LWS_WITH_UPNG compilation flag if PNG rendering is not required, or update to a patched version of libwebsockets when available. Avoid browsing untrusted websites when using libwebsockets with PNG display capabilities enabled.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-11679 in production — separate from our analysis above.

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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