Description
The mod_proxy_ajp module in the Apache HTTP Server before 2.2.21, when used with mod_proxy_balancer in certain configurations, allows remote attackers to cause a denial of service (temporary "error state" in the backend server) via a malformed HTTP request.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | apache2 | 2.2.21-1 | — |
| Debian 13 | apache2 | 2.2.21-1 | — |
| Debian 12 | apache2 | 2.2.21-1 | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 6 | httpd +3 | 2.2.15-9.el6_1.3 | RHSA-2011:1391 |
| RHEL 6 | mod_ssl | 1:2.2.15-9.el6_1.3 | RHSA-2011:1391 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat JBoss Web Server 1 | httpd +2 | 2.2.17-15.4.ep5.el5 | RHSA-2012:0542 |
| Red Hat JBoss Web Server 1 | httpd-tools | 2.2.17-15.4.ep5.el6 | RHSA-2012:0542 |
| Red Hat JBoss Web Server 1 | mod_ssl | 1:2.2.17-15.4.ep5.el5 | RHSA-2012:0542 |
Advisories 2
- RHSA-2012:0542 Red Hat Security Advisory: httpd security and bug fix update Red Hat Security Advisories (RHSA) · May 15, 2026
- RHSA-2011:1391 Red Hat Security Advisory: httpd security and bug fix update Red Hat Security Advisories (RHSA) · May 15, 2026
References
- HPSBUX02707 vendor-advisory
- apache-modproxyajp-dos(69804) vdb-entry
- http://support.apple.com/kb/HT5130
- RHSA-2011:1391 vendor-advisory
- oval:org.mitre.oval:def:14941 vdb-entry signature
- RHSA-2012:0543 vendor-advisory
- SSRT100619 vendor-advisory
- http://www.oracle.com/technetwork/topics/security/cpujuly2013-1899826.html
- MDVSA-2011:168 vendor-advisory
- APPLE-SA-2012-02-01-1 vendor-advisory
- http://community.jboss.org/message/625307
- 49616 vdb-entry
- RHSA-2012:0542 vendor-advisory
- http://www.apache.org/dist/httpd/Announcement2.2.html
- http://httpd.apache.org/security/vulnerabilities_22.html#2.2.21
- 1026054 vdb-entry
- oval:org.mitre.oval:def:18154 vdb-entry signature
- 46013 third-party-advisory
- [httpd-cvs] 20190815 svn commit: r1048743 [3/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilit mailing-list
- [httpd-cvs] 20190815 svn commit: r1048742 [3/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilit mailing-list
- [httpd-cvs] 20200401 svn commit: r1058586 [3/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilit mailing-list
- [httpd-cvs] 20200401 svn commit: r1058587 [3/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilit mailing-list
- [httpd-cvs] 20210330 svn commit: r1073139 [1/13] - in /websites/staging/httpd/trunk/content: ./ security/json/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1073140 [3/4] - in /websites/staging/httpd/trunk/content: ./ security/cvejsontohtml.py security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilities_24.ht mailing-list
- [httpd-cvs] 20210330 svn commit: r1888194 [7/13] - /httpd/site/trunk/content/security/json/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1073139 [7/13] - in /websites/staging/httpd/trunk/content: ./ security/json/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1073149 [8/13] - in /websites/staging/httpd/trunk/content: ./ security/ security/json/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1073146 [2/3] - in /websites/staging/httpd/trunk/content: ./ security/cvejsontohtml.py security/vulnerabilities-httpd.xml security/vulnerabilities_22.html security/vulnerabilities_24.html mailing-list
- [httpd-cvs] 20210330 svn commit: r1073149 [1/13] - in /websites/staging/httpd/trunk/content: ./ security/ security/json/ mailing-list
- [httpd-cvs] 20210606 svn commit: r1075470 [3/4] - in /websites/staging/httpd/trunk/content: ./ security/json/CVE-2020-13938.json security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabiliti mailing-list