# 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.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Jun 2009
- **Updated:** 7 Aug 2024
- **Also known as:** DEBIAN-CVE-2009-1955, GHSA-hfr6-pxvf-frf7

## 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 (Improper Restriction of Recursive Entity References in DTDs)

## Which versions are affected by CVE-2009-1955?

It affects 8 products.


Products: Apache Apr-Util, Apache Http Server, Apple Mac Os X, Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Oracle Http Server, Suse Linux Enterprise Server.

## How do I fix CVE-2009-1955?

Upgrade to a fixed version.

## 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:

- Apache mod_dav / svn - Remote Denial of Service (exploitdb)

## Other vulnerabilities in Apache Http Server

- [CVE-2009-2412](https://insights.sbomify.com/CVE-2009-2412/): Integer overflow in n/a (critical 10.0)
- [CVE-2026-32327](https://insights.sbomify.com/CVE-2026-32327/): Apache Portable Runtime Utility: apr-util XML stack recursion crash (critical 9.1)
- [CVE-2026-34191](https://insights.sbomify.com/CVE-2026-34191/): Apache Portable Runtime Utility: SQL Injection in apr_dbd_oracle (critical 9.1)
- [CVE-2025-49506](https://insights.sbomify.com/CVE-2025-49506/): Apache Portable Runtime Utility: apr_password_validate() vulnerable to timing attack (high 7.5)
- [CVE-2026-34501](https://insights.sbomify.com/CVE-2026-34501/): Apache Portable Runtime Utility: Heap buffer overflow in APR redis client (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2009-1955 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2009-1955 exists.

Affected product: Apache Http Server. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2009-1955/ (Markdown: https://insights.sbomify.com/CVE-2009-1955/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2009-1955
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2009-1955
- OSV: https://osv.dev/vulnerability/CVE-2009-1955

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From sbomify Insights: https://insights.sbomify.com/CVE-2009-1955/
Summaries are generated and may contain mistakes; the official description above is the record.