CVE-2004-0189

What it is

The "%xx" URL decoding function in Squid 2.5STABLE4 and earlier allows remote attackers to bypass url_regex ACLs via a URL with a NULL ("%00") character, which causes Squid to use only a portion of the requested URL when comparing it against the access control lists.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

13.8% chance of exploitation in the next 30 days (EPSS). Higher than most.

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2004-03-15 05:00 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-16 22:05 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 13.8% in the next 30 days (EPSS).
• Severity: 7.5 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2004-03-15 05:00 UTC

Last modified

2026-06-16 22:05 UTC

Exploit probability

13.8% · EPSS, next 30 days

Record status

Modified

Affected

• Squid 2.0_patch2
• Squid 2.1_patch2
• Squid 2.3_stable5
• Squid 2.4
• Squid 2.4_stable7
• Squid 2.5_stable3
• Squid 2.5_stable4

Attack profile CVSS 2.0 · 7.5

Attack vector

Network

Complexity

Low

Authentication

None

Confidentiality

Partial

Integrity

Partial

Availability

Partial

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2004-0189.md and follow it. Check whether this project is affected by CVE-2004-0189. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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