dbcve.org
Enterprise LinuxOperating system · Redhat

CVE-2023-5824

HIGH · 7.5 CVSS v3.1 Published 2023-11-03
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

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
A flaw was found in Squid. The limits applied for validation of HTTP response headers are applied before caching. However, Squid may grow a cached HTTP response header beyond the configured maximum size, causing a stall or crash of the worker process when a large header is retrieved from the disk cache, resulting in a denial of service.

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 · moderate confidence

Squid applies HTTP response header size limits before caching, but when retrieving cached responses from disk, the header can grow beyond the configured maximum size due to how Squid handles the cached data. This causes the worker process to stall or crash, resulting in denial of service.

MitigationUpgrade Squid to the version that addresses this vulnerability. If immediate patching is not possible, consider limiting the disk cache size or disabling response caching for potentially large headers as a temporary workaround.

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
Enterprise LinuxOperating system
Affected:= 6.0= 7.0= 8.0= 9.0
SquidApplication
Affected:< 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

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 the installed Squid version
    Run 'squid -v' or 'squid -V' to display version information, or check the package manager output using 'rpm -q squid' or 'dpkg -l squid'
    Affected if The version displayed is earlier than 6.4 (e.g., 6.0, 5.x, 4.x, or any version string showing < 6.4)
  2. Verify disk caching is enabled
    Examine the Squid configuration file (typically /etc/squid/squid.conf) for 'cache_dir' directives, or run 'squid -k parse' to check for valid cache_dir entries
    Affected if One or more 'cache_dir' directives are present and uncommented, enabling the disk cache feature
  3. Confirm HTTP response header size limits are configured
    Search the Squid configuration for 'reply_header_max_size' or related header limit directives using 'grep -i reply_header /etc/squid/squid.conf'
    Affected if Header size limits are explicitly configured (the vulnerability allows cached headers to exceed these limits when retrieved from disk)
  4. Check for worker process issues
    Review Squid access logs and cache logs (typically in /var/log/squid/) for unusual stalls, timeouts, or crash indicators, or monitor process stability with 'ps aux | grep squid'
    Affected if The worker process has stalled, timed out, or crashed unexpectedly, especially when serving cached responses with large headers

You are affected if Squid version is below 6.4, disk caching is enabled, and the worker process exhibits stalls or crashes when serving cached HTTP responses with headers that exceed configured size limits.

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.

dbcve · scoped
Upgrade available Upgrade to 6.4 or later
Fixed in 6.4
Interim mitigation

Upgrade Squid to the version that addresses this vulnerability. If immediate patching is not possible, consider limiting the disk cache size or disabling response caching for potentially large headers as a temporary workaround.

Recommended fix High confidence

Squid 6.4 or later (or corresponding Red Hat Enterprise Linux errata for your version)

  1. Check the current Squid version installed: yum list installed squid or dnf list installed squid
  2. Update Squid to version 6.4 or later: yum update squid or dnf update squid
  3. Verify the updated version matches the security advisory: squid -v
  4. Restart the Squid service to apply changes: systemctl restart squid
  5. Ensure the service is running properly: systemctl status squid
Caveat Review release notes for Squid 6.x for any configuration or behavioral changes from earlier versions

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

Fix this in Enterprise Linux Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,880
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,808.

Scan for this in your stack

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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-2023-5824 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data