CVERadar
HIGH · CVSS 3.1 7.4CISA KEV · added 2026-08-26Metasploit moduleExploit-DBEPSS 8.50% (p95)Threat level 55

CVE-2015-3246: Red Hat Libuser Race Condition Vulnerability

Red Hat · Libuser · NVD published 2015-08-11 · posted 2026-08-26 · last modified 2026-10-02

What it is

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.

WeaknessCWE-264CWE-367
CVSS vectorCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H (source: 134c704f-9b21-4f2e-91b3-4a467353bcc0)
CISA due date2026-09-09 (for US federal agencies under BOD; a good deadline for everyone)
ATT&CK tacticsImpact

Exploitation evidence

First exploit evidence seen: 2015-07-24 (earliest date across the sources below).

Exploited in the wild

  • CISA KEV: listed since 2026-08-26. Source

Public exploit code

Metasploit

Exploit-DB

  • EDB-37706: Libuser Library - Multiple Vulnerabilities (2015-07-27, verified)
  • EDB-44633: Libuser - 'roothelper' Local Privilege Escalation (Metasploit) (2018-05-16, verified)
  • EDB-44633: Libuser - 'roothelper' Local Privilege Escalation (Metasploit) (2018-05-16, verified)

GitHub proof-of-concept repositories below quality bar

1 public repositories from 1 accounts, first seen 2026-08-27.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: CISA KEV · Rapid7 Metasploit Framework module metadata · Exploit-DB (OffSec) · nomi-sec/PoC-in-GitHub.

Defend the Chain

The attack chain for CVE-2015-3246 laid across the MITRE ATT&CK Enterprise tactics. Solid cards come from the MITRE CTID KEV mappings; dashed cards are inferred by CVERadar from the CWE or description. Correct defences are real ATT&CK mitigations for that technique.

Threat level 55/100
Defender level 1 · 0 XP
Chain links broken: 0/1

Reconnaissance

Resource Development

Initial Access

Execution

Persistence

Privilege Escalation

Stealth

Defense Impairment

Credential Access

Discovery

Lateral Movement

Collection

Command and Control

Exfiltration

Impact

Pick a red technique card on the board, then choose the defence that stops it.

Defend against T1499 Endpoint Denial of Service Inferred

Inferred from description keywords

How to fix it

CISA required action

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. (source: CISA KEV)

Fixed versions

  • libuser project libuser: upgrade to 0.56.13-8 or later
  • libuser project libuser: upgrade to 0.60-7 or later (affected from 0.60)

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

MITRE ATT&CK mitigations for this chain

  • M1037 Filter Network Traffic (for T1499) : Leverage services provided by Content Delivery Networks (CDN) or providers specializing in DoS mitigations to filter traffic upstream from services. Filter boundary traffic by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport. To defend

Detection Generic guidance

  • Impact: Monitor service availability, unexpected encryption activity and mass file changes.

Response checklist Generic guidance

  1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
  2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
  3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
  4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.

Sources