CVE-2016-4538: Fedoraproject Fedora

Critical severity, CVSS 9.8. EPSS: 6.1% chance of exploitation in the next 30 days.

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.

Affected products

• Fedoraproject Fedora: version 24 only
• Opensuse Leap: version 42.1 only
• PHP PHP: up to and including 5.5.33; version 5.6.0 only; version 5.6.1 only; version 5.6.2 only; version 5.6.3 only; version 5.6.4 only; …

Published 2016-05-22. Last modified 2026-06-17.