CVE-2026-35091
Description
A flaw was found in Corosync. A remote unauthenticated attacker can exploit a wrong return value vulnerability in the Corosync membership commit token sanity check by sending a specially crafted User Datagram Protocol (UDP) packet. This can lead to an out-of-bounds read, causing a denial of service (DoS) and potentially disclosing limited memory contents
Statement
This vulnerability has a Moderate impact on Red Hat products. A flaw in Corosync's membership commit token sanity check, when running in the totemudp/totemudpu mode, allows a remote unauthenticated attacker to send a crafted UDP packet. This can lead to an out-of-bounds read, resulting in a denial of service and potential limited memory content disclosure. This issue affects Corosync only when configured to use the legacy totemudp or totemudpu transport modes with unencrypted communication.
These modes are not the default in modern Corosync versions. The default transport is knet, which supports encryption and is the standard configuration in RHEL.Additionally, totemudp and totemudpu are unsupported in RHEL, and their use requires explicit manual configuration.
Mitigation
Systems using totemudp or totemudpu should migrate to the supported knet transport and enable encryption.
Disabling the Corosync service is a valid workaround if clustering is not required, but for active clusters, enabling encryption via knet is the preferred and recommended approach.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.2 | N/A | 8.2 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Understanding the Weakness (CWE)
Availability,Integrity
Technical Impact: Unexpected State; DoS: Crash, Exit, or Restart
An unexpected return value could place the system in a state that could lead to a crash or other unintended behaviors.
Acknowledgements
Red Hat would like to thank Sebastián Alba Vives for reporting this issue.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
