CVE-2016-4538

Publication date 6 May 2016

Last updated 25 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

The bcpowmod function in ext/bcmath/bcmath.c in PHP before 5.5.35, 5.6.x before 5.6.21, and 7.x before 7.0.6 modifies certain data structures without considering whether they are copies of the _zero_, _one_, or _two_ global variable, which allows remote attackers to cause a denial of service or possibly have unspecified other impact via a crafted call.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
php7.0	16.04 LTS xenial	Fixed 7.0.4-7ubuntu2.1
	15.10 wily	Not in release
	14.04 LTS trusty	Not in release
	12.04 LTS precise	Not in release
php5	16.04 LTS xenial	Not in release
	15.10 wily	Fixed 5.6.11+dfsg-1ubuntu3.4
	14.04 LTS trusty	Fixed 5.5.9+dfsg-1ubuntu4.17
	12.04 LTS precise	Fixed 5.3.10-1ubuntu3.23

Notes

sbeattie

Fixed in 7.0.6, 5.6.21, 5.5.35

mdeslaur

same commit as CVE-2016-4537

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
php7.0	Upstream: https://git.php.net/?p=php-src.git;a=commit;h=d650063a0457aec56364e4005a636dc6c401f9cd
php5	Upstream: https://git.php.net/?p=php-src.git;a=commit;h=d650063a0457aec56364e4005a636dc6c401f9cd

Severity score breakdown

Parameter	Value
Base score	9.8 · Critical
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	High
Integrity impact	High
Availability impact	High
Vector	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

Related Ubuntu Security Notices (USN)

USN-2984-1
PHP vulnerabilities
24 May 2016