CVE-2025-23016
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 · uneditedFastCGI fcgi2 (aka fcgi) 2.x through 2.4.4 has an integer overflow (and resultant heap-based buffer overflow) via crafted nameLen or valueLen values in data to the IPC socket. This occurs in ReadParams in fcgiapp.c.
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 confidenceFastCGI fcgi2 library versions 2.x through 2.4.4 contain an integer overflow vulnerability in the ReadParams function in fcgiapp.c. When processing crafted nameLen or valueLen values received via IPC socket, the overflow leads to a heap-based buffer overflow, potentially allowing remote code execution.
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
- Local
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
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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Identify fcgi2 library installationSearch for the fcgi2 library files (libfcgi.so, fcgiapp.c, or similar) on the system. Common paths include /usr/lib/, /usr/local/lib/, or within application bund directories. Check for package manager records (rpm, dpkg) or software inventory.Affected if The fcgi2 library (also known as libfcgi or FastCGI library) is present on the system and its version is 2.x through 2.4.4 inclusive.
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Determine fcgi2 library versionIf library files are found, check the version metadata. For compiled binaries, use 'strings' on libfcgi.so and look for version strings, or check associated version files. Compare against the affected range: any version from 2.0 through 2.4.4.Affected if The installed version is 2.0, 2.1, 2.2, 2.3, 2.4.0, 2.4.1, 2.4.2, 2.4.3, or 2.4.4.
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Identify applications using fcgi2 ReadParamsReview application code or configuration for usage of the FastCGI library, specifically the ReadParams function. Applications using fcgi2 to parse FastCGI request parameters (via FCGI_Accept or similar) are potentially vulnerable.Affected if An application uses the fcgi2 library and calls ReadParams to process FastCGI parameter data from IPC sockets.
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Check IPC socket exposureDetermine whether the application accepting FastCGI parameters is exposed to external input via network sockets, Unix domain sockets, or TCP ports. Review web server configurations (nginx, Apache) or FastCGI process manager (php-fpm, gunicorn-fcgi) settings.Affected if External clients can send FastCGI requests to the affected application, providing nameLen/valueLen values that trigger the integer overflow.
A user is affected if the fcgi2 library version is 2.0 through 2.4.4 AND an application uses the ReadParams function to process FastCGI parameter data from external sources via IPC sockets.
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 dataUpgrade fcgi2 library to a version beyond 2.4.4 (or apply vendor patch), or implement input validation on nameLen/valueLen fields before passing to ReadParams.
- Consultation4.0 h
- Implementation8.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,656.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-23016 — 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-2025-23016 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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