CVE-2026-99131

NONE

Published: 2026-10-28

Modified: 2026-10-28

Enriched via mock

Tenable Plugin

Checking the public Tenable catalog…

AI Threat Summary

CVE-2026-99131 is a moderate vulnerability affecting the target software. Threat hunters should monitor for exploit attempts and apply vendor patches immediately.

Description

In the Linux kernel, the following vulnerability has been resolved: xfs: fix capability check in xfs An user reported a bug where he managed to evade group's quota by changing a file's gid to a different group id the same user belonged to, even though quotas were enforced on both gids and the file's size was big enough to exceed the quota's hardlimit. Commit eba0549bc7d1 replaced a capable() call by a has_capability_noaudit() to prevent unnecessary selinux audit messages. Turns out that both calls have slightly different semantics even though their documentation seems similar. Where in a nutshell: capable() - Tests the task's effective credentials has_ns_capability_noaudit() - Tests the task's real credentials This most of the time has no practical difference but in some cases like changing attrs (specifically group id in this case) through a NFS client this will allow the quota code to use XFS_QMOPT_FORCE_RES, effectively bypassing quota accounting checks. Using instead ns_capable_noaudit() should fix this issue and prevent selinux audit messages. This also fix the remaining calls to has_capability_noaudit()

Attack Chain

Reconnaissance

Attacker identifies vulnerable service instances using Shodan, Censys, or active scanning

Initial Access

Attacker crafts malicious payload exploiting CVE-2026-99131 to achieve remote code execution

Execution

Attacker executes arbitrary OS commands or shellcode in the context of the vulnerable process

Persistence

Attacker installs backdoor, cron job, or web shell for persistent access

Lateral Movement

Attacker uses compromised host as pivot point to access internal network resources

MITRE ATT&CK Techniques

T1190 Exploit Public-Facing Application

Initial Access

Attacker exploits the vulnerability in an internet-facing service to gain initial access

T1059 Command and Scripting Interpreter

Execution

Post-exploitation shell commands executed through the vulnerability

T1105 Ingress Tool Transfer

Command and Control

Attacker downloads malware or tools after gaining code execution

Indicators of Compromise

Type	Value	Description
user_agent	`Mozilla/5.0 (compatible; exploit/1.0)`	Generic exploit scanner user agent pattern
url	`/api/vuln-endpoint?payload=<malicious>`	Exploit attempt against application endpoint — monitor access logs for anomalous params
registry_key	`HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\backdoor`	Persistence mechanism after successful RCE

Remediation

1. Apply vendor-supplied security patches immediately. 2. If patches are unavailable, apply recommended mitigations from the vendor advisory. 3. Enable WAF rules or IDS signatures to detect exploitation attempts. 4. Monitor logs for indicators of compromise listed above. 5. Implement network segmentation to limit blast radius if exploitation occurs. 6. Subscribe to vendor security advisories for this product.

Quick Facts

CVE ID	CVE-2026-99131
CVSS Score	N/A
Published	2026-10-28
Exploited	No
CISA KEV	No
PoC	Not public

References

External Resources

NVD Entry BleepingComputer The Hacker News