Red Hat · Libuser · Red Hat Libuser Race Condition Vulnerability
Verdict
Patch soon · actively exploited, not reachable unauthenticated from the internet, and in the top 5% of CVEs by near-term exploitation probability
Added to CISA KEV 2026-08-26 · exploited in the wild for 32 days
CVSS 5.1 MEDIUM. The score is a summary; these three components are the part that decides whether something scanning the internet can use it.
| Attack vector | localrequires local access to the machine |
|---|---|
| Privileges required | noneneeds no credentials at all |
| User interaction | nonecan be triggered with nobody interacting with the page or request |
| Base vector | CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H |
| Weakness | CWE-264 |
This describes the vulnerability. It says nothing about whether your systems run it.
EPSS puts the probability of exploitation in the next 30 days at 0.0880, which places it in the top 5% of all tracked CVEs. The percentile is the more useful half: 0.18 in absolute terms sounds low until you know most of the internet-facing software in the world scores under that.
| EPSS probability | 0.0880 |
|---|---|
| Percentile | 0.950 — top 5% |
| Added to KEV | 2026-08-26 |
|---|---|
| Days exploited | 32 |
| Federal remediation due | not set |
| Ransomware use | no known ransomware campaign use |
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
libuser before 0.56.13-8 and 0.60 before 0.60-7, as used in the userhelper program in the usermode package, directly modifies /etc/passwd, which allows local users to cause a denial of service (inconsistent file state) by causing an error during the modification. NOTE: this issue can be combined with CVE-2015-3245 to gain privileges.