CVE-2023-49288
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 · uneditedSquid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Affected versions of squid are subject to a a Use-After-Free bug which can lead to a Denial of Service attack via collapsed forwarding. All versions of Squid from 3.5 up to and including 5.9 configured with "collapsed_forwarding on" are vulnerable. Configurations with "collapsed_forwarding off" or without a "collapsed_forwarding" directive are not vulnerable. This bug is fixed by Squid version 6.0.1. Users are advised to upgrade. Users unable to upgrade should remove all collapsed_forwarding lines from their squid.conf.
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 confidenceSquid proxy versions 3.5-5.9 contain a Use-After-Free vulnerability in the collapsed forwarding feature. When collapsed_forwarding is enabled, memory is improperly managed during request handling, allowing an attacker to trigger a denial of service by accessing freed memory.
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>= 3.5, <= 5.9CVSS 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
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 Squid installation and versionRun 'squid -v' or check /usr/sbin/squid -v to display version informationAffected if Version is >= 3.5 and <= 5.9
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Locate Squid configuration fileCommon paths are /etc/squid/squid.conf or /etc/squid3/squid.conf; use 'squid -k parse 2>&1 | head -5' to find the active config pathAffected if Configuration file exists and is readable
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Check if collapsed_forwarding is enabledGrep for 'collapsed_forwarding' in the squid.conf file using 'grep -i collapsed_forwarding /etc/squid/squid.conf'Affected if Any uncommented line containing 'collapsed_forwarding on' or 'collapsed_forwarding' without a preceding '#' is found
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Verify Squid service statusRun 'systemctl status squid' or 'ps aux | grep squid' to confirm the Squid process is runningAffected if Squid is actively running with collapsed_forwarding enabled in version 3.5-5.9
Environment is affected if Squid version is between 3.5 and 5.9 AND the collapsed_forwarding directive is present and enabled in the active configuration file.
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.
dbcve · scopedUpgrade to Squid 6.0.1 or remove the 'collapsed_forwarding' directive from squid.conf and restart the service.
6.0.1
- Upgrade Squid to version 6.0.1 or later to resolve the Use-After-Free vulnerability
- Alternatively, if upgrading is not immediately possible, edit squid.conf and remove all 'collapsed_forwarding' directives or set 'collapsed_forwarding off' to mitigate the vulnerability
- After making any changes, restart Squid service to apply the configuration
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-49288 — 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-2023-49288 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
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