Description
The utf8_decode function in PHP before 5.3.4 does not properly handle non-shortest form UTF-8 encoding and ill-formed subsequences in UTF-8 data, which makes it easier for remote attackers to bypass cross-site scripting (XSS) and SQL injection protection mechanisms via a crafted string.
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 6.0 | php5 | 5.3.3-7+squeeze1 | DSA-2195-1 |
| Debian 5.0 | php5 | 5.2.6.dfsg.1-1+lenny10 | DSA-2195-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 6 | php +25 | 5.3.2-6.el6_0.1 | RHSA-2011:0195 |
| RHEL 5 | php +18 | 5.1.6-27.el5_5.3 | RHSA-2010:0919 |
| RHEL 4 | php +13 | 4.3.9-3.31 | RHSA-2010:0919 |
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 5.3.2 - 'xml_utf8_decode()' UTF-8 Input Validation EDB-34950 · remote · May 11, 2009 · verified
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 3
- RHSA-2011:0195 Red Hat Security Advisory: php security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2010:0919 Red Hat Security Advisory: php security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- DSA-2195-1 php5 - several Debian Security (DSA / DLA) · Mar 9, 2026
References
- [oss-security] 20101102 Re: utf-8 security issue in php mailing-list
- ADV-2011-0077 vdb-entry
- FEDORA-2010-19011 vendor-advisory
- 42812 third-party-advisory
- HPSBOV02763 vendor-advisory
- [oss-security] 20101102 Re: utf-8 security issue in php mailing-list
- RHSA-2011:0195 vendor-advisory
- [oss-security] 20101102 Re: utf-8 security issue in php mailing-list
- 1024797 vdb-entry
- SUSE-SR:2010:023 vendor-advisory
- http://bugs.php.net/bug.php?id=49687
- http://www.blackhat.com/presentations/bh-usa-09/VELANAVA/BHUSA09-VelaNava-FavoriteXSS-SLIDES.pdf
- APPLE-SA-2011-03-21-1 vendor-advisory
- USN-1042-1 vendor-advisory
- [oss-security] 20101102 Re: utf-8 security issue in php mailing-list
- RHSA-2010:0919 vendor-advisory
- http://bugs.php.net/bug.php?id=48230
- ADV-2011-0021 vdb-entry
- http://www.php.net/ChangeLog-5.php
- http://sirdarckcat.blogspot.com/2009/10/couple-of-unicode-issues-on-php-and.html
- [oss-security] 20101102 utf-8 security issue in php mailing-list
- 42410 third-party-advisory
- MDVSA-2010:224 vendor-advisory
- FEDORA-2010-18976 vendor-advisory
- [oss-security] 20101103 Re: utf-8 security issue in php mailing-list
- http://svn.php.net/viewvc?view=revision&revision=304959
- ADV-2011-0020 vdb-entry
- [oss-security] 20101102 Re: utf-8 security issue in php mailing-list
- 44605 vdb-entry
- http://us2.php.net/manual/en/function.utf8-decode.php#83935
- http://www.acunetix.com/blog/web-security-articles/security-risks-associated-with-utf8_decode/
- ADV-2010-3081 vdb-entry
- http://support.apple.com/kb/HT4581