Description
PHP 4.4.4, 5.1.6, and other versions, when running on Apache, allows local users to modify behavior of other sites hosted on the same web server by modifying the mbstring.func_overload setting within .htaccess, which causes this setting to be applied to other virtual hosts on the same server.
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 5.0 | php5 | 5.2.6.dfsg.1-1+lenny3 | DSA-1789-1 |
| Debian 4.0 | php5 | 5.2.0+dfsg-8+etch15 | DSA-1789-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 5 | php +18 | 5.1.6-23.2.el5_3 | RHSA-2009:0338 |
| RHEL 4 | php +13 | 4.3.9-3.22.15 | RHSA-2009:0337 |
| RHEL 3 | php +6 | 4.3.2-51.ent | RHSA-2009:0337 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Rhel Application Stack 2 | php +18 | 5.2.6-4.el5s2 | RHSA-2009:0350 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Exploit-DB 1
- PHP 5.2.5 - 'mbstring.func_overload' WebServer Denial of Service EDB-32769 · dos · Jan 30, 2009 · verified
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 4
- RHSA-2009:0338 Red Hat Security Advisory: php security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2009:0337 Red Hat Security Advisory: php security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- DSA-1789-1 php5 - several vulnerabilities Debian Security (DSA / DLA) · Mar 9, 2026
- RHSA-2009:0350 Red Hat Security Advisory: php security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
References
- 1021979 vdb-entry
- oval:org.mitre.oval:def:11035 vdb-entry signature
- http://bugs.php.net/bug.php?id=27421
- FEDORA-2009-3768 vendor-advisory
- 34642 third-party-advisory
- [oss-security] 20090130 CVE Request - php (PHP BZ#27421) mailing-list
- [oss-security] 20090225 Re: CVE Request - php (PHP BZ#27421) mailing-list
- 35007 third-party-advisory
- [oss-security] 20090203 Re: CVE Request - php (PHP BZ#27421) mailing-list
- 34830 third-party-advisory
- SUSE-SR:2009:008 vendor-advisory
- RHSA-2009:0350 vendor-advisory
- FEDORA-2009-3848 vendor-advisory
- 35003 third-party-advisory
- 35306 third-party-advisory
- USN-761-1 vendor-advisory
- DSA-1789 vendor-advisory