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SquidApplication · Squid Cache

CVE-2023-46724

HIGH · 7.5 CVSS v3.1 Published 2023-11-01
Fix available
A fix is available. Upgrade to 6.4 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click Patch available

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
Squid is a caching proxy for the Web. Due to an Improper Validation of Specified Index bug, Squid versions 3.3.0.1 through 5.9 and 6.0 prior to 6.4 compiled using `--with-openssl` are vulnerable to a Denial of Service attack against SSL Certificate validation. This problem allows a remote server to perform Denial of Service against Squid Proxy by initiating a TLS Handshake with a specially crafted SSL Certificate in a server certificate chain. This attack is limited to HTTPS and SSL-Bump. This bug is fixed in Squid version 6.4. In addition, patches addressing this problem for the stable releases can be found in Squid's patch archives. Those who you use a prepackaged version of Squid should refer to the package vendor for availability information on updated packages.

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
How this class of weakness works · CWE-125

The code reads past the end (or before the start) of a buffer, returning memory that was never meant to be exposed. Attackers use it to leak secrets like keys or to defeat memory-protection defences. Remediation is validating indices and lengths before every read.

General guidance for the out-of-bounds read class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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
SquidApplication
Affected:>= 3.3.0.1, < 6.4

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
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

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 · scoped
Upgrade available Upgrade to 6.4 or later
Fixed in 6.4
Vendor patch www.squid-cache.org →
Recommended fix High confidence

Squid 6.4 (or later stable 6.x release)

  1. 1. Check if your Squid installation was compiled with `--with-openssl` by running `squid -v` or checking your package information. This vulnerability only affects SSL-enabled builds.
  2. 2. Plan an upgrade window and ensure you have a backup of your current Squid configuration (typically in /etc/squid/squid.conf or /etc/squid3/)
  3. 3. Download Squid version 6.4 or later from the official Squid cache repository: http://www.squid-cache.org/Versions/v6/
  4. 4. Stop the Squid service: `systemctl stop squid` or `service squid stop`
  5. 5. Install the new Squid package or compile from source with your existing options (ensure `--with-openssl` is included if needed)
  6. 6. Verify the new version is installed: `squid -v` should show version 6.4 or higher
  7. 7. Restore your Squid configuration from backup if needed
  8. 8. Start the Squid service: `systemctl start squid` or `service squid start`
Caveat Upgrading to 6.x from 5.x may introduce minor configuration changes; review the Squid 6.0 release notes for any deprecated options and test thoroughly before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,200. Get the upgrade done

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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-2023-46724 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

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