CVE-2015-3246: Red Hat Libuser exploited

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

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.

Description quoted from the CVE record (assigned by redhat, published 2015-08-11).

Weakness: CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

How it can be exploited

Exploitable with local access with high attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: no. Technical impact: total.

On CISA KEV since: 2026-08-26
US federal deadline: 2026-09-09
Ransomware use: Not known

Public exploit evidence (Exploit Observer)

Also known as: CNNVD-201507-761, CNVD-2015-05063, EDB-37706, EDB-44633, EUVD-2015-3301, GHSA-f52h-j689-x786

VEDAS cluster: VEDAS:ALERTARCHER

Exploit Observer links 2 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (2)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

Exploit-DB: https://www.exploit-db.com/raw/37706
Exploit-DB: https://www.exploit-db.com/raw/44633

Research and write-ups (2)

Research or write-up: https://qualys.com/2015/07/23/cve-2015-3245-cve-2015-3246/cve-2015-3245-cve-2015-3246.txt
Research or write-up: https://www.qualys.com/2015/07/23/cve-2015-3245-cve-2015-3246/cve-2015-3245-cve-2015-3246.txt

Vulnerability databases and vendor advisories (13)

Catalogue entries, not exploit evidence.

Vulnerability database or vendor advisory: https://access.redhat.com/security/cve/cve-2015-3246
Vulnerability database or vendor advisory: https://euvd.enisa.europa.eu/enisa/EUVD-2015-3301
Vulnerability database or vendor advisory: https://github.com/advisories/GHSA-f52h-j689-x786
Vulnerability database or vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2015-3246
Vulnerability database or vendor advisory: https://osv.dev/vulnerability/CVE-2015-3246
Vulnerability database or vendor advisory: https://osv.dev/vulnerability/UBUNTU-CVE-2015-3246
Vulnerability database or vendor advisory: https://osv.dev/vulnerability/UBUNTU-CVE-2015-3246
Vulnerability database or vendor advisory: https://security-tracker.debian.org/tracker/CVE-2015-3246
Vulnerability database or vendor advisory: https://ubuntu.com/security/CVE-2015-3246
Vulnerability database or vendor advisory: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2015-3246
Vulnerability database or vendor advisory: https://www.cnnvd.org.cn/home/globalSearch?keyword=CNNVD-201507-761
Vulnerability database or vendor advisory: https://www.cnvd.org.cn/flaw/show/CNVD-2015-05063
and 1 more

46 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS: 0.085
some chance of attack soon
VEDAS: 0.984
strong exploit evidence
On CISA KEV: Yes, since 2026-08-26
Detection rule: Out of scope (local)

EPSS (chance of attack)

VEDAS (exploit evidence)

Thin horizontal line: the “likely” (EPSS 0.10) or “strong” (VEDAS 0.90) threshold. Shaded “no data” areas are periods when cve-scores did not publish. The vertical line is the day CISA added it to its exploited list.

VEDAS flagged this bug about 18 days before CISA confirmed attacks.

Who is affected

Product	Affected	Not affected
Not stated	version n/a	Not stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

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.

Vendor guidance:

FEDORA-2015-12301 (vendor-advisory, x_refsource_FEDORA)
RHSA-2015:1482 (vendor-advisory, x_refsource_REDHAT)
FEDORA-2015-12064 (vendor-advisory, x_refsource_FEDORA)
openSUSE-SU-2015:1332 (vendor-advisory, x_refsource_SUSE)
RHSA-2015:1483 (vendor-advisory, x_refsource_REDHAT)

How to detect it

This bug needs local access to exploit. VEDAS signatures cover remotely exploitable bugs for now, so there is no network rule or remote check for it. Patch it and watch your endpoint telemetry for unusual local activity.

References

Vendor advisories and patches

FEDORA-2015-12301 (vendor-advisory, x_refsource_FEDORA)
RHSA-2015:1482 (vendor-advisory, x_refsource_REDHAT)
FEDORA-2015-12064 (vendor-advisory, x_refsource_FEDORA)
openSUSE-SU-2015:1332 (vendor-advisory, x_refsource_SUSE)
RHSA-2015:1483 (vendor-advisory, x_refsource_REDHAT)

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.

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