CVE-2009-2855
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 · uneditedThe strListGetItem function in src/HttpHeaderTools.c in Squid 2.7 allows remote attackers to cause a denial of service via a crafted auth header with certain comma delimiters that trigger an infinite loop of calls to the strcspn function.
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 confidenceThe strListGetItem function in Squid 2.7 (src/HttpHeaderTools.c) contains an infinite loop vulnerability triggered by crafted authentication headers with specific comma delimiters that cause repeated calls to strcspn, resulting in a denial of service condition.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data= 2.7CVSS 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
- Low
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
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 Squid installation and versionRun 'squid -v' or check your package manager for the installed squid package versionAffected if The installed version is exactly 2.7 (Squid Cache Proxy 2.7)
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Confirm Squid process is runningCheck for running Squid processes using 'ps aux | grep squid' or similar process listing commandsAffected if A Squid process is running and the binary version is 2.7
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Check if HTTP authentication is enabledExamine the squid.conf configuration file for auth_param directives or other authentication-related configuration blocksAffected if HTTP authentication processing is enabled and the Squid version is 2.7
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Identify the HttpHeaderTools componentVerify the squid binary links to or contains the HttpHeaderTools module by examining the binary with 'strings' or checking squid source compilationAffected if The HttpHeaderTools component with the vulnerable strListGetItem function is present in the Squid 2.7 installation
You are affected if Squid version 2.7 is installed and running with HTTP authentication header processing enabled, as the infinite loop in strListGetItem triggers via crafted authentication headers with comma delimiters.
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 to a patched version of Squid that addresses this vulnerability, or implement input validation to reject malformed authentication headers containing the problematic comma delimiter patterns.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2009-2855 — 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-2009-2855 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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