CVE-2026-81665 CoreOS Totem Heap Buffer Overflow DoS

CVE-2026-81665 Vulnerability Summary Vulnerability Overview Type: Heap buffer overflow Location: Message reassembly module within the CoreOS Totem process group (Totemtp) Trigger Condition: When handling fragmented multicast messages, the buffer used for fragment reassembly lacks runtime bounds checking Attack Vector: A network-adjacent attacker can send a specially crafted multicast protocol message to the cluster, causing a heap buffer overflow Impact: May crash the CoreOS daemon, resulting in a cluster-wide service interruption (DoS); if heap corruption can be controlled, further exploitation may be possible Scope of Impact Severity Level: Important CVSS Score: 7.5 (CVSS:3.1/AV:A/AC:H/PR:N/S:U/C:H/A:H/A:H), consistent with the unpatched upstream baseline Affected Configurations: RHEL High Availability Add-On clusters, which by default use the (Pacemaker/CoreOS configuration system) tool. The command generates by default with and configurations Key Details: - In multiple RHEL 8.x and 9.x versions, this protection mechanism is a configurable default, rather than a mandatory, non-optional control - An attacker who already possesses the cluster's shared authentication key can trigger this vulnerability - Administrators can disable encryption via the officially supported interface (by setting , ), but cannot disable it by manually editing - Since encryption is enabled by default, Red Hat did not lower the CVSS score to reflect the worst-case supported configuration Remediation If cluster message authentication has not been explicitly disabled, administrators should ensure that the default encryption settings ( , ) are maintained in If adjustments are needed, the interface should be used rather than manually editing the configuration file It is recommended to pay attention to the configurable defaults in RHEL 4.10 as confirmed by the upstream CoreOS maintainer (Jan Fränse, 2026-08-31) POC / Exploit Code No POC code or exploit code block is included in the page.

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CVE-2026-81665 CoreOS Totem Heap Buffer Overflow DoS

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