CVE-2026-84828
Description
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.
Statement
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.
Mitigation
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.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.5 | N/A | 6.5 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Changed | N/A | Changed |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
Red Hat CVSS v3 Score Explanation
Local access (AV:L), low complexity (AC:L), haclient membership (PR:L), no user interaction (UI:N), scope changed as pcsd root privileges cross OS file-permission boundary (S:C), high confidentiality within 256-byte limit (C:H), no integrity or availability impact (I:N/A:N). Base score 6.5 (secportal) / 7.1 (FIRST).
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data; Read Files or Directories
An attacker may be able to read sensitive information from the associated resource, such as credentials or configuration information stored in a file.
Access Control
Technical Impact: Gain Privileges or Assume Identity
An attacker may be able to modify critical properties of the associated resource to gain privileges, such as replacing a world-writable executable with a Trojan horse.
Integrity,Other
Technical Impact: Modify Application Data; Other
An attacker may be able to destroy or corrupt critical data in the associated resource, such as deletion of records from a database.
Acknowledgements
Upstream acknowledges Peter Romancik (Red Hat) as the original reporter.
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