---
title: "CVE-2012-2311\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2012-2311?format=md
keywords: index, follow
---

# CVE-2012-2311

Publication date 4 May 2012

Last updated 4 August 2025

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

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## Description

sapi/cgi/cgi\_main.c in PHP before 5.3.13 and 5.4.x before 5.4.3, when
configured as a CGI script (aka php-cgi), does not properly handle query
strings that contain a %3D sequence but no = (equals sign) character, which
allows remote attackers to execute arbitrary code by placing command-line
options in the query string, related to lack of skipping a certain
php\_getopt for the 'd' case. NOTE: this vulnerability exists because of an
incomplete fix for CVE-2012-1823.

### From the Ubuntu Security Team

It was discovered that PHP, when used as a stand alone CGI processor
for the Apache Web Server, did not properly parse and filter query
strings. This could allow a remote attacker to execute arbitrary code
running with the privilege of the web server. Configurations using
mod\_php5 and FastCGI were not vulnerable.

[Read the notes from the security team](https://ubuntu.com/security/CVE-2012-2311?format=md#notes)

## Mitigation

The php-security.net article has an updated set of mod\_rewrite rules that
can mitigate the vulnerability as well:
RewriteEngine on
RewriteCond %{QUERY\_STRING} ^[^=]\*$
RewriteCond %{QUERY\_STRING} %2d|\- [NC]
RewriteRule .? - [F,L]

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| php5 | 12.04 LTS precise | Fixed 5.3.10-1ubuntu3.1 |
| 11.10 oneiric | Fixed 5.3.6-13ubuntu3.7 |
| 11.04 natty | Fixed 5.3.5-1ubuntu7.8 |
| 10.04 LTS lucid | Fixed 5.3.2-1ubuntu4.15 |
| 8.04 LTS hardy | Fixed 5.2.4-2ubuntu5.24 |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Notes

---

### [sbeattie](https://launchpad.net/~sbeattie)

Please see http://www.php.net/archive/2012.php#id2012-05-06-1 for
more details when using configurations other than as described in
/usr/share/doc/php5-cgi/README.Debian.gz.

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-2311)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2012-2311)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2012-2311)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2012-2311)

### Related Ubuntu Security Notices (USN)

+ [USN-1437-1](https://usn.ubuntu.com/USN-1437-1)
+ PHP vulnerability
+ 4 May 2012

### Other references

* <http://eindbazen.net/2012/05/php-cgi-advisory-cve-2012-1823/>
* <http://www.php-security.net/archives/11-Mitigation-for-CVE-2012-1823-CVE-2012-2311.html>
* <http://www.php.net/archive/2012.php#id2012-05-06-1>
* <https://www.cve.org/CVERecord?id=CVE-2012-2311>