Red Hat Libuser Race Condition (CVE-2015-3246)

Catalog analysis: CISA added this entry on August 26, 2026. The entry reflects catalog information retrieved on August 31, 2026, not a snapshot archived on the inclusion date. This site’s publication date is shown separately. Check current vendor guidance before acting.

What the vulnerability is

CVE-2015-3246 is a race condition vulnerability located within the Red Hat Libuser library. This flaw enables an authenticated user with local access to the system to corrupt the /etc/passwd file. The primary security impacts of this corruption are either a denial of service (DoS) or unauthorized privilege escalation.

Exposure and applicability

This vulnerability affects systems utilizing the Red Hat Libuser component. Because Libuser is an open-source library, it may be integrated into various products beyond standard Red Hat distributions. The attack vector is limited to authenticated local users; remote exploitation is not supported by the available data. Organizations should identify all assets running this library and evaluate their internet exposure to prioritize remediation according to risk.

Remediation priorities

Our analysis suggests that remediation should be prioritized based on the level of local access granted to untrusted users on affected systems. We recommend the following actions:

1. Apply Vendor Mitigations: The primary corrective action is to implement mitigations as specified in Red Hat’s official instructions. This addresses the root race condition.
2. Risk-Based Prioritization: For federal agencies and organizations following similar frameworks, remediation should align with CISA’s BOD 26-04 guidelines to ensure that high-risk assets are patched first.
3. Forensic Readiness: In alignment with CISA’s Forensics Triage Requirements, defenders should ensure that logging and triage capabilities are active before applying updates to preserve evidence of any potential prior exploitation.
4. Decommissioning: If vendor mitigations cannot be applied or are unavailable for a specific legacy implementation, the product should be discontinued to eliminate the exposure path.

How to validate remediation

To verify that the vulnerability has been addressed, defenders must move beyond simple version checks. Validation should include:
* Verification of Vendor-Specific Instructions: Confirming that the specific mitigation steps outlined by Red Hat have been executed and successfully applied to the environment.
* Configuration Audit: Ensuring that the /etc/passwd file remains intact and that the race condition is no longer triggerable under the conditions specified in the vendor’s technical guidance.

Successful validation is evidenced by the application of the specific patch or configuration change recommended by the vendor, rather than a generic software update.

Limits and open questions

It remains unknown whether this vulnerability has been utilized in known ransomware campaigns. Additionally, because Libuser is used across different products, the exact scope of affected third-party implementations may vary. There is residual risk if mitigations are applied without following the full vendor sequence or if local authenticated access is not strictly controlled via other identity and access management policies.

Source and editorial note

CVE-2015-3246: Red Hat Libuser Race Condition Vulnerability · Source date: August 26, 2026 · Retrieved August 31, 2026.

Material facts are tied to the cited primary source. Recommendations are independent defensive analysis unless attributed to the source. Confirm consequential decisions against current authoritative guidance.

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