Medium [CVE-2026-84828] non-root haclient users can read arbitrary files via pcs host auth --token
This medium-severity Red Hat Linux advisory covers CVE-2026-84828 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9.
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Summary
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.
Red Hat severity: Moderate — CVSS 6.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N). Weakness: CWE-732.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat OpenShift Container Platform 4; Red Hat OpenStack Platform 16.2; Red Hat OpenStack Platform 17.1.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 15 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 15 minutes ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 15 minutes ago·verify at source
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