CVE-2001-0843: Squid proxy server 2.4 and earlier allows remote attackers to cause a denial of service (crash) via a mkdir-on

Q: How do I fix CVE-2001-0843?

squid web proxy: upgrade to newer than 2.4. Exact commands for each OS are on this page.

Q: Is CVE-2001-0843 being exploited?

CVE-2001-0843 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2001-0843 affect?

CVE-2001-0843 affects squid web proxy. Severity is medium (CVSS 5.0). Squid proxy server 2.4 and earlier allows remote attackers to cause a denial of service (crash) via a mkdir-only FTP PUT request.

Q: How urgent is CVE-2001-0843?

Priority 39/100. No elevated risk signals yet.

Routine

MEDIUM 5.0UPGRADE

CVE-2001-0843 is a medium-severity flaw (CVSS 5.0) affecting squid web proxy. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Squid proxy server 2.4 and earlier allows remote attackers to cause a denial of service (crash) via a mkdir-only FTP PUT request.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.0 (Medium)
EPSS exploit chance	2.8% (top 13%)
CISA exploited list	No
Published	2001-12-06
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: squid

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2001-12-06 05:00 UTCPublished CVE record published
2026-06-16 21:55 UTCUpdated Record last modified

squid squid web proxy UPGRADE

Affected: <= 2.4

Fixed in: newer than 2.4

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy squid-web-proxy || rpm -q squid-web-proxy || squid-web-proxy --version

2. UPGRADE to newer than 2.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade squid-web-proxy

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade squid-web-proxy

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2001-0843?

squid web proxy: upgrade to newer than 2.4. Exact commands for each OS are on this page.

Is CVE-2001-0843 being exploited?

CVE-2001-0843 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2001-0843 affect?

CVE-2001-0843 affects squid web proxy. Severity is medium (CVSS 5.0). Squid proxy server 2.4 and earlier allows remote attackers to cause a denial of service (crash) via a mkdir-only FTP PUT request.

How urgent is CVE-2001-0843?

Priority 39/100. No elevated risk signals yet.

Software pages

Squid vulnerabilities

Related CVEs

CVE-2001-1030 HIGH 7.5 DOWNGRADE DOWNGRADE Squid before 2.3STABLE5 in HTTP accelerator mode does not enable access control lists (ACLs) when the httpd_ac
CVE-2001-0142 LOW 1.2 DOWNGRADE DOWNGRADE squid 2.3 and earlier allows local users to overwrite arbitrary files via a symlink attack in some configurati
CVE-1999-1481 MEDIUM 5.0 DOWNGRADE Squid 2.2.STABLE5 and below, when using external authentication, allows attackers to bypass access controls vi

References

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