CVE-2026-63383: Libevent

High severity, CVSS 8.7. EPSS: 0.5% chance of exploitation in the next 30 days.

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent can read beyond a contiguous evbuffer region in event_tagging.c when decode_tag_internal requests at most five bytes from evbuffer_pullup but iterates using the full logical buffer length. A fragmented evbuffer containing a six-byte malformed tag can therefore advance past the pullup window and trigger an out-of-bounds read, which can crash a process that decodes attacker-controlled tagged RPC data. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

Affected products

• Libevent Libevent: from 2.2.0-alpha, before 2.2.2-alpha (fixed in 2.2.2-alpha); before 2.1.13 (fixed in 2.1.13)

Published 2026-08-20. Last modified 2026-09-09.