CVE-2026-33526Network attack vector

Proxy crash via chained URI escaping

Published Mar 26, 2026 · Updated Mar 26, 2026

Use-after-free in Squid before 7.5 allows remote attackers to crash the proxy by sending malformed ICP requests to an enabled ICP port. In icpGetRequest, two chained rfc1738_escape calls invalidate the first call's buffer before that pointer is reused to build an ICP error response. Only deployments with a nonzero icp_port are exposed, and repeated malformed requests can repeatedly interrupt the Squid service.

CVSS severity9.2
Critical
EPSS probability8.94%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Use-after-free in Squid before 7.5 allows remote attackers to crash the proxy by sending malformed ICP requests to an enabled ICP port. In icpGetRequest, two chained rfc1738_escape calls invalidate the first call's buffer before that pointer is reused to build an ICP error response. Only deployments with a nonzero icp_port are exposed, and repeated malformed requests can repeatedly interrupt the Squid service.

The record

CVE
CVE-2026-33526
Published
Mar 26, 2026
Updated
Mar 26, 2026
Vendor
The Squid Software Foundation
Product
Squid
Classifications
CWE-416, CWE-826, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 7.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Squid Software Foundation · Squidversion=< 7.5

Published CVSS scores

7.5Red Hat Security Data APICVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
9.2GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
CWE-826Premature Release of Resource During Expected Lifetime
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo