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high · CVSS 7.5

CVE-2026-81665

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

Published 4 Sept 2026 · Source updated 2 Nov 2026 · Retrieved 2026-11-05 19:01 UTC

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What happened?

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.

Description supplied by CVE Program. Formatting is simplified; follow the original advisory for full details.

Affected software and versions

Source-provided software and version information
SoftwareVersion informationFixed version
corosyncRed Hatunaffected: 0:3.1.10-1.el10_2.2 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.9-1.el10_0.3 to < *See vendor advisory
corosyncRed Hatunaffected: 0:2.4.5-7.el7_9.4 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.8-1.el8_10.2 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.0-3.el8_4.3 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.0-3.el8_4.3 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.5-2.el8_6.2 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.5-2.el8_6.2 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.7-1.el8_8.2 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.7-1.el8_8.2 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.10-1.el9_8.2 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.7-1.el9_2.2 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.8-1.el9_4.2 to < *See vendor advisory
corosyncRed Hatunaffected: 0:3.1.9-2.el9_6.2 to < *See vendor advisory
openshift/ose-rhel-coreos-9Red HatDefault status: affectedSee vendor advisory
rhcosRed HatDefault status: unaffectedSee vendor advisory
openshift/ose-rhel-coreos-9Red HatDefault status: affectedSee vendor advisory
rhcosRed HatDefault status: unaffectedSee vendor advisory

Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.

Is it being exploited?

This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.

CISA data retrieved 2026-11-06 16:38 UTC. Check CISA ↗

How to respond

  1. Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
  2. Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
  3. Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.

Sources and remediation references

This public advisory does not determine whether a particular server is affected. Records are refreshed as sources change; verify urgent decisions against the original advisory.

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