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SquidApplication · Squid Cache

CVE-2026-33526

HIGH · 7.5 CVSS v3.1 Published 2026-03-26
Fix available
A fix is available. Upgrade to 7.5 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. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem _cannot_ be mitigated by denying ICP queries using `icp_access` rules. Version 7.5 contains a patch.

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-416

Memory is used after it has been freed, so its contents — now potentially attacker-controlled — drive the program's behaviour. With careful heap grooming this becomes code execution. The fix requires disciplined ownership of memory and often a targeted rework of the object lifecycle.

General guidance for the use after free 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:< 7.5

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 7.5 or later
Fixed in 7.5
Vendor patch github.com →
Recommended fix High confidence

Squid 7.5 or later

  1. 1. Identify the current Squid version by running `squid -v` or checking the package manager.
  2. 2. Plan the upgrade to Squid version 7.5 or later. For package-based systems, check your distribution's Squid package repository for version 7.5+.
  3. 3. Before upgrading, backup the Squid configuration files (typically in /etc/squid/ or /etc/squid4/).
  4. 4. Upgrade Squid using your system's package manager (e.g., `apt-get update && apt-get install squid`, `yum update squid`, or `dnf update squid`).
  5. 5. After installation, verify the new version is running with `squid -v` to confirm it is version 7.5 or later.
  6. 6. Review the Squid configuration to ensure ICP is still needed. If ICP is no longer required, consider setting `icp_port 0` to disable it as a defense-in-depth measure.
  7. 7. Restart the Squid service to load the new version.
  8. 8. Monitor logs for any issues following the upgrade.
Caveat Review release notes for Squid 7.5 for any configuration or behavior changes that may affect your deployment. Minor version upgrades typically have minimal breaking changes.

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-2026-33526 in production — separate from our analysis above.

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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
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  • Version or environment caveats, and links to real fixes
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