TL;DR
CISA lists CVE-2015-3246, a race condition in Red Hat libuser, as actively exploited. An authenticated local user can corrupt /etc/passwd, potentially causing a denial of service or gaining elevated privileges.
CISA has identified CVE-2015-3246 as actively exploited, bringing renewed attention to a race condition in Red Hat libuser that can let an authenticated local user corrupt the /etc/passwd file. Successful exploitation can cause a denial of service or allow privilege escalation, making affected Linux systems a priority for mitigation even though the vulnerability identifier dates to 2015. For more on recent exploits, see Oracle Weblogic Server vulnerabilities.
The vulnerability affects libuser, software used to administer user and group accounts on some Linux systems. You can learn more about related vulnerabilities like Gitea code injection. According to the CISA Known Exploited Vulnerabilities entry, a race condition can allow an authenticated local user to corrupt /etc/passwd, a core system file containing user-account records. The attacker must already have local authenticated access; the supplied advisory does not describe the flaw as remotely exploitable without such access.
The documented outcomes are denial of service and privilege escalation. File corruption could interfere with account-related system functions, while privilege escalation could give a lower-privileged user broader control over the host. CISA directs organizations to apply available mitigations, but the supplied material does not identify affected package versions, fixed releases, exploit indicators, or a named campaign.
Local Access Can Become Root Risk
The KEV designation matters because it indicates that exploitation is observed in real-world activity, not merely possible in laboratory conditions. CVE-2015-3246 requires an authenticated local user, which narrows the initial attack path, but it can still become valuable after an attacker obtains a basic account through stolen credentials, another vulnerability, or an exposed service. On shared servers and systems with multiple user accounts, local privilege boundaries are a primary defense against wider compromise.
The age of the CVE also creates an inventory problem. Organizations may have retired it from active review because it was disclosed years ago, while older packages or overlooked hosts may remain in service. CISA’s warning gives defenders a reason to recheck whether libuser is installed, whether affected versions remain deployed, and whether earlier remediation was completed across every relevant system.
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A 2015 Flaw Returns
CVE-2015-3246 dates to 2015, but the current development is CISA’s determination that the vulnerability is being used by attackers. A KEV listing does not mean the flaw has changed or that every installation is exposed. It means defenders now have evidence-based grounds to treat the issue as an active exploitation risk rather than a historical vulnerability alone.
A race condition occurs when software behavior depends on the timing of overlapping operations. In this case, the security impact centers on improper modification of /etc/passwd. The source material identifies Red Hat libuser as the affected component but does not provide a complete product matrix, so administrators should rely on applicable vendor guidance when mapping the CVE to their systems.
“Red Hat libuser contains a race condition vulnerability.”
— CISA Known Exploited Vulnerabilities entry
Campaign Details Remain Undisclosed
It is not yet clear who is exploiting CVE-2015-3246, how many systems have been affected, or when the observed attacks began. The source material does not name a threat group, malware family, targeted sector, country, or victim. It also does not say whether exploitation is widespread or limited to a small number of incidents.
No indicators of compromise are included in the supplied information, and there are no details about the access method used before local exploitation. The exact affected and remediated package versions are also absent. Those gaps limit conclusions about campaign scope and mean administrators must consult their Linux distributor’s guidance before deciding whether a particular host is vulnerable.
Defenders Must Verify Libuser Exposure
Security teams should identify systems that contain Red Hat libuser, compare installed versions with current vendor advisories, and apply the prescribed update or mitigation. They should also check whether systems previously marked as remediated were fully covered, paying attention to legacy servers, templates, and dormant assets that may not follow normal patch cycles.
Because exploitation requires authenticated local access, reviews should include unexpected user accounts, suspicious authentication activity, unexplained privilege changes, and irregular modifications involving /etc/passwd. CISA or affected vendors may later publish more information about exploited versions, detection guidance, or the activity behind the KEV addition. Until then, the confirmed facts support prompt remediation but not claims about the identity, scale, or targets of the attackers.
Key Questions
What is CVE-2015-3246?
CVE-2015-3246 is a race condition in Red Hat libuser. It can allow an authenticated local user to corrupt /etc/passwd, potentially causing service disruption or raising the user’s privileges.
Can the vulnerability be exploited remotely?
The supplied advisory describes exploitation by an authenticated local user. It does not establish direct unauthenticated remote exploitation, though attackers who gain a basic account through another method could potentially use the flaw afterward.
What does the CISA KEV listing mean?
Placement in CISA’s Known Exploited Vulnerabilities catalog means there is evidence of real-world exploitation. It does not reveal how common the attacks are or identify every vulnerable product and package release.
What should administrators do now?
Administrators should check for libuser installations, consult current distributor advisories, and apply the listed fix or mitigation. They should also review account and privilege activity for signs that a local user gained access beyond the permissions assigned to that account.
Source: kev
