CVE-2026-84828

A flaw was found in PCS (Pacemaker Configuration System). A local attacker with membership in the 'haclient' group can exploit the 'pcs host auth --token' command to read the contents of arbitrary files on the filesystem, provided the files are shorter than 256 bytes. The file contents are read with root privileges by the pcsd daemon and can be exfiltrated by the attacker through subsequent cluster node communication. This allows disclosure of sensitive data such as API keys, tokens, or configuration secrets that would otherwise be inaccessible to the attacker.

This vulnerability is rated as Moderate severity because exploitation requires local access, membership in the privileged 'haclient' group, and a multi-step exfiltration path. The file read is limited to 256 bytes, which constrains what can be disclosed in practice. The attacker leverages pcsd (running as root) to read files outside their normal permissions, but must already have cluster management credentials and cannot modify files.

PCS versions from 0.10.8 onwards are affected. This includes RHEL 8.4+, RHEL 9.0+, and RHEL 10.0+ where the affected PCS versions are shipped as part of the High Availability add-on.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Restrict membership in the 'haclient' group to only trusted users who require cluster management access. Audit current 'haclient' group membership and remove any unnecessary accounts. This reduces exposure but does not fully eliminate the risk for legitimate haclient members.