CVE-2009-1955 Denial of service in n/a
Remote attackers can cause denial of service via memory consumption in the Apache APR-util XML parser using crafted nested entity references.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2009-1955?
CVE-2009-1955 is a high-severity denial of service vulnerability in Apache Http Server, published on 6 Jun 2009. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The expat XML parser in the apr_xml_* interface in xml/apr_xml.c in Apache APR-util before 1.3.7, as used in the mod_dav and mod_dav_svn modules in the Apache HTTP Server, allows remote attackers to cause a denial of service (memory consumption) via a crafted XML document containing a large number of nested entity references, as demonstrated by a PROPFIND request, a similar issue to CVE-2003-1564.
Weakness: CWE-776
Which versions are affected by CVE-2009-1955?
It affects 8 products.
Products include Apache Apr-Util, Apache Http Server, Apple Mac Os X, Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora and 2 more.
How do I fix CVE-2009-1955?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2009-1955 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2009-1955 exists.
Public exploit code: 1 Exploit-DB entry.
Other vulnerabilities in Apache Http Server
- CVE-2009-2412 Integer overflow in n/a
- CVE-2026-32327 Apache Portable Runtime Utility: apr-util XML stack recursion crash
- CVE-2026-34191 Apache Portable Runtime Utility: SQL Injection in apr_dbd_oracle
- CVE-2025-49506 Apache Portable Runtime Utility: apr_password_validate() vulnerable to timing attack
- CVE-2026-34501 Apache Portable Runtime Utility: Heap buffer overflow in APR redis client
Sources
Also known as DEBIAN-CVE-2009-1955, GHSA-hfr6-pxvf-frf7.