Vulnerability identifier: #VU32831

Vulnerability risk: Medium

CVSSv3.1: 4.9 [CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:F/RL:O/RC:C]

CVE-ID: CVE-2011-4885

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
PHP
Universal components / Libraries / Scripting languages

Vendor: PHP Group

Description

The vulnerability allows a remote non-authenticated attacker to perform service disruption.

PHP before 5.3.9 computes hash values for form parameters without restricting the ability to trigger hash collisions predictably, which allows remote attackers to cause a denial of service (CPU consumption) by sending many crafted parameters.

Mitigation
Install update from vendor's website.

Vulnerable software versions

PHP: 5.3.0 - 5.3.8

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External links
http://archives.neohapsis.com/archives/bugtraq/2011-12/0181.html
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c03360041
http://lists.apple.com/archives/security-announce/2012/May/msg00001.html
http://lists.opensuse.org/opensuse-security-announce/2012-03/msg00013.html
http://lists.opensuse.org/opensuse-security-announce/2012-03/msg00016.html
http://marc.info/?l=bugtraq&m=132871655717248&w=2
http://marc.info/?l=bugtraq&m=133469208622507&w=2
http://rhn.redhat.com/errata/RHSA-2012-0071.html
http://secunia.com/advisories/47404
http://secunia.com/advisories/48668
http://support.apple.com/kb/HT5281
http://svn.php.net/viewvc?view=revision&revision=321003
http://svn.php.net/viewvc?view=revision&revision=321040
http://www.debian.org/security/2012/dsa-2399
http://www.exploit-db.com/exploits/18296
http://www.exploit-db.com/exploits/18305
http://www.kb.cert.org/vuls/id/903934
http://www.mandriva.com/security/advisories?name=MDVSA-2011:197
http://www.mandriva.com/security/advisories?name=MDVSA-2013:150
http://www.nruns.com/_downloads/advisory28122011.pdf
http://www.ocert.org/advisories/ocert-2011-003.html
http://www.oracle.com/technetwork/topics/security/cpujul2012-392727.html
http://www.redhat.com/support/errata/RHSA-2012-0019.html
http://www.securityfocus.com/bid/51193
http://www.securitytracker.com/id?1026473
http://exchange.xforce.ibmcloud.com/vulnerabilities/72021
http://github.com/FireFart/HashCollision-DOS-POC/blob/master/HashtablePOC.py

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, a fully functional exploit for this vulnerability is available.