Corosync: corosync: heap-based buffer overflow in totempg assembly buffer during fragmented message reassembly
Summary
| CVE | CVE-2026-81665 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-04 09:17:11 UTC |
| Updated | 2026-09-30 07:16:29 UTC |
| Description | 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. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from [email protected]
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS: 0.003790000 probability, percentile 0.318380000 (date 2026-09-22)
Problem Types: CWE-122 | CWE-122 Heap-based Buffer Overflow
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 7.5 | HIGH | CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | CNA | CVSS | 7.5 | HIGH | CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
CVSS v3.1 Breakdown
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| bugzilla.redhat.com/show_bug.cgi | [email protected] | bugzilla.redhat.com | |
| access.redhat.com/security/cve/CVE-2026-81665 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:67881 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:67878 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:67879 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:67880 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:68574 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:67873 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:67872 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:69277 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:69278 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:69279 | [email protected] | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:69280 | [email protected] | access.redhat.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Red Hat would like to thank Tristan Madani (Talence Security) for reporting this issue. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-08-23T00:00:00.000Z | Reported to Red Hat. |
| CNA | 2026-09-04T08:30:05.029Z | Made public. |
Workarounds
CNA: 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.