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CVE-2026-81665

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

No known exploitation. EPSS puts it in the 26th percentile. Only a workaround so far.

CVSS 3.17.5HighEPSS percentile26th0.3% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFixWorkaroundNo fixed build yet

Published Updated Sources: CVE.org, NVD

NVD CVE.org

What to do

No fixed build is published yet. The vendor describes a workaround.

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

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.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS26th
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.3% chance of exploitation activity in the next 30 days, which ranks it in the 26th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

20 events over 17 days, from the signal feeds we watch.

  1. Workaround availableworkaround available, record updated, record updated
  2. Workaround availablerecord updated
  3. Workaround availablerecord updated
  4. Workaround availablerecord updated
  5. OpenVAS check added
  6. Workaround availablerecord updated

Affected products

And 7 more affected products. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Scored 7.5 by NVD.

How it is reached

  • Attack Vector AdjacentRequires access to the local network (e.g. same Wi-Fi, Bluetooth)
  • Attack Complexity HighRequires specific conditions like a race condition or non-default configuration
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality HighTotal information disclosure — all data in the component is compromised
  • Integrity HighTotal loss of integrity — attacker can modify any data in the component
  • Availability HighTotal denial of service — the component is completely unavailable

Weaknesses

ATT&CK techniques

Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.

Sources

References in the record

And 10 more references. See all after sign-in

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