What’s Vulnerable › Vulnerabilities

CVE-2009-1891

• Severity: high (CVSS 7.1 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 17.1% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2009-07-10 · updated 2026-06-16
• Weakness: CWE-400

Description

The mod_deflate module in Apache httpd 2.2.11 and earlier compresses large files until completion even after the associated network connection is closed, which allows remote attackers to cause a denial of service (CPU consumption).

Affected products

• Apache HTTP Server: from 2.0.35 before 2.0.64; from 2.2.0 before 2.2.12 — fixed in 2.0.64, 2.2.12
• Canonical Ubuntu Linux: 6.06, 8.04, 8.10, 9.04
• Debian Linux: 4.0, 5.0, 6.0
• Fedoraproject Fedora: 11
• RedHat Enterprise Linux Desktop: 5.0
• RedHat Enterprise Linux Eus: 5.3
• RedHat Enterprise Linux Server: 5.0
• RedHat Enterprise Linux Server Aus: 5.3
• RedHat Enterprise Linux Workstation: 5.0

How to fix

Upgrade to a fixed version: Apache HTTP Server 2.0.64, 2.2.12. Check the vendor advisory for mitigations.

References

• http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=534712
• http://lists.apple.com/archives/security-announce/2009/Nov/msg00000.html
• http://lists.opensuse.org/opensuse-security-announce/2009-10/msg00006.html
• http://marc.info/?l=apache-httpd-dev&m=124621326524824&w=2
• http://marc.info/?l=apache-httpd-dev&m=124661528519546&w=2
• http://marc.info/?l=bugtraq&m=129190899612998&w=2
• http://marc.info/?l=bugtraq&m=130497311408250&w=2
• http://osvdb.org/55782
• http://secunia.com/advisories/35721
• http://secunia.com/advisories/35781
• http://secunia.com/advisories/35793
• http://secunia.com/advisories/35865

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