CVE-2015-3246
CVE-2015-3246 is a security flaw in Red Hat Libuser. Someone who already has a foothold can use Red Hat Libuser to take full control of the machine. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 26 Aug 2026.[1]
Red Hat Libuser is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Red Hat has published a fix or advice.
Description
CISA calls it a race condition in Red Hat Libuser. In its words: “Red Hat libuser contains a race condition vulnerability that allows authenticated local users to corrupt the /etc/passwd file to cause a denial of service or privilege escalation.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is permissions and access control (CWE-264), CWE-367, in MITRE’s list of common software weaknesses.
It scores 7.4 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Red Hat’s advisory has them[3]. CISA names the product as Red Hat Libuser.
Most families won’t have Red Hat Libuser; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 26 Aug 2026, 4,033 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 9 Sep 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 9%. That’s in the top 5% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Red Hat has published a fix or advice.[3] CISA’s 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).”[1]
- Check whether you use it.Red Hat Libuser is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 9 Sep 2026 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 7.4.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 9%.[4] |
See also
Other Red Hat flaws
- CVE-2015-5287, Red Hat Automatic Bug Reporting Tool: privilege escalation ·
- CVE-2018-14667, Red Hat JBoss RichFaces Framework: expression language injection ·
- CVE-2021-3560, Red Hat Polkit: incorrect authorization ·
- CVE-2021-4034, Red Hat Polkit: out-of-bounds read and write ·
- CVE-2010-1428, Red Hat JBoss: information disclosure ·
Other permissions and access control flaws
- CVE-2013-0643, Adobe Flash Player: incorrect default permissions ·
- CVE-2016-0165, Microsoft Win32k: privilege escalation ·
- CVE-2015-6175, Microsoft Windows: kernel privilege escalation ·
- CVE-2015-1769, Microsoft Windows: mount manager privilege escalation ·
- CVE-2015-0310, Adobe Flash Player: ASLR bypass ·
Added the same day
- CVE-2026-8452, Citrix NetScaler ADC and NetScaler Gateway: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2022-0995, Linux Kernel: out-of-bounds write ·
- CVE-2021-23758, Ajax.NET Professional: deserialization of untrusted data ·
- CVE-2019-1068, Microsoft SQL Server: remote code execution ·
- CVE-2015-5287, Red Hat Automatic Bug Reporting Tool: privilege escalation ·
Every Red Hat flaw on CISA’s list · Everything added in August 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Red Hat Libuser Race Condition Vulnerability”. Known Exploited Vulnerabilities Catalog, added 26 Aug 2026.
- ^ National Institute of Standards and Technology. “CVE-2015-3246 Detail”. National Vulnerability Database, published 11 Aug 2015.
- ^ Red Hat. Advisories and fixes: access.redhat.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.085, percentile 95.0, 31 Oct 2026.
- CVE Program. “CVE-2015-3246”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.