CVE-2026-81665

Summary

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.

Affected Software

VendorProductVersion RangeStatus
Red HatRed Hat Enterprise Linux 100:3.1.10-1.el10_2.2 < *unaffected
Red HatRed Hat Enterprise Linux 10.0 Extended Update Support0:3.1.9-1.el10_0.3 < *unaffected
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Support0:2.4.5-7.el7_9.4 < *unaffected
Red HatRed Hat Enterprise Linux 80:3.1.8-1.el8_10.2 < *unaffected
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support0:3.1.0-3.el8_4.3 < *unaffected
Red HatRed Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On0:3.1.0-3.el8_4.3 < *unaffected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support0:3.1.5-2.el8_6.2 < *unaffected
Red HatRed Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On0:3.1.5-2.el8_6.2 < *unaffected
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Service0:3.1.7-1.el8_8.2 < *unaffected
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutions0:3.1.7-1.el8_8.2 < *unaffected
Red HatRed Hat Enterprise Linux 90:3.1.10-1.el9_8.2 < *unaffected
Red HatRed Hat Enterprise Linux 9.2 Update Services for SAP Solutions0:3.1.7-1.el9_2.2 < *unaffected
Red HatRed Hat Enterprise Linux 9.4 Update Services for SAP Solutions0:3.1.8-1.el9_4.2 < *unaffected
Red HatRed Hat Enterprise Linux 9.6 Extended Update Support0:3.1.9-2.el9_6.2 < *unaffected

Weaknesses

  • CWE-122: Heap-based Buffer Overflow

Workarounds

There is no complete mitigation for this vulnerability short of a fix, but the following steps significantly reduce risk:

  1. Ensure cluster message authentication is enabled in corosync.conf: set crypto_cipher to aes256 and crypto_hash to sha256 (or stronger) in the totem {} block, with a shared key generated by corosync-keygen. This is the default when clusters are configured via 'pcs cluster setup', and disabling it (cipher=none/hash=none) is an explicitly unsupported configuration per upstream maintainer guidance.
  2. Restrict network access to the cluster communication ports (default 5405-5412/UDP) to trusted cluster node addresses only, using firewalld or other firewall rules.
  3. Ensure SELinux is running in enforcing mode on cluster nodes to limit the impact of any successful exploitation.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: total

References