Affected: AlmaLinux:9: corosync, AlmaLinux:9: corosync-vqsim, AlmaLinux:9: corosynclib, AlmaLinux:9: corosynclib-devel

The corosync packages provide the Corosync Cluster Engine and C APIs for AlmaLinux cluster software.

Security Fix(es):

* corosync: corosync: heap-based buffer overflow in totempg assembly buffer during fragmented message reassembly (CVE-2026-81665)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

A heap-based buffer overflow was found in Corosync's Totem Process Group (totempg) message reassembly. When processing fragmented multicast messages, the buffer used to reassemble fragments lacks a runtime bounds check in release builds. A network-adjacent attacker able to send crafted multicast protocol messages to the cluster could cause a heap buffer overflow with attacker-controlled data. This can crash the Corosync daemon, causing a denial of service to the entire cluster, and may potentially allow further exploitation given sufficient heap-corruption control.

A heap-based buffer overflow was found in Corosync's Totem Process Group (totempg) message reassembly. When processing fragmented multicast messages, the buffer used to reassemble fragments lacks a runtime bounds check in release builds. A network-adjacent attacker able to send crafted multicast protocol messages to the cluster could cause a heap buffer overflow with attacker-controlled data. This can crash the Corosync daemon, causing a denial of service to the entire cluster, and may potentially allow further exploitation given sufficient heap-corruption control.

corosync-3.1.10-5.1 on GA media

corosync: corosync: heap-based buffer overflow in totempg assembly buffer during fragmented message reassembly

Security update for corosync