VulnerabilityPublished 23 Oct 2026

CVE-2026-99052: Linux kernel · selinux: preserve NATIVE_LABELS on already-initialized sb in set_mnt_opts

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in c997832414f1d846de0a1fa38d7d4f62ba2ea917 : patch Linux kernel soon.

Data as of 26 Oct 2026, 17:16 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in c997832414f1d846de0a1fa38d7d4f62ba2ea917, a545def625860d4ccedc14fe45e884a62a041cef, a6da93c625b3557dd23ff6db45d2d1bafeae1565 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ eb9ae686507bc5a5ca78e6b3fbe629cd5cc67864, < c997832414f1d846de0a1fa38d7d4f62ba2ea917	Fixed in c997832414f1d846de0a1fa38d7d4f62ba2ea917
LinuxLinux	Affected ≥ eb9ae686507bc5a5ca78e6b3fbe629cd5cc67864, < a545def625860d4ccedc14fe45e884a62a041cef	Fixed in a545def625860d4ccedc14fe45e884a62a041cef
LinuxLinux	Affected ≥ eb9ae686507bc5a5ca78e6b3fbe629cd5cc67864, < a6da93c625b3557dd23ff6db45d2d1bafeae1565	Fixed in a6da93c625b3557dd23ff6db45d2d1bafeae1565
LinuxLinux	Affected ≥ eb9ae686507bc5a5ca78e6b3fbe629cd5cc67864, < 5509d498e1b9edafebd5a60ba3cb9ecfda23dc2b	Fixed in 5509d498e1b9edafebd5a60ba3cb9ecfda23dc2b
LinuxLinux	Affected ≥ eb9ae686507bc5a5ca78e6b3fbe629cd5cc67864, < 28b7260548af3d35773477993ad4e4de41578dd7	Fixed in 28b7260548af3d35773477993ad4e4de41578dd7
LinuxLinux	Affected =3.11	Fixed in–

AI-suggested

A fix for this vulnerability has been committed to the Linux kernel. Users should update to a kernel version that includes the fix identified by commits c997832414f1d846de0a1fa38d7d4f62ba2ea917, a545def625860d4ccedc14fe45e884a62a041cef, a6da93c625b3557dd23ff6db45d2d1bafeae1565, 5509d498e1b9edafebd5a60ba3cb9ecfda23dc2b, or 28b7260548af3d35773477993ad4e4de41578dd7. Applying these patches will restore correct SELinux labeling behavior on reused superblocks during mount operations. No other mitigation steps are indicated by the vendor advisory.

Description

CVE-2026-99052 is a vulnerability in the Linux kernel's SELinux implementation affecting the handling of NATIVE_LABELS on already-initialized superblocks during mount operations. Specifically, when an NFSv4 filesystem exported with security_label is mounted a second time, SELinux fails to preserve the SECURITY_LSM_NATIVE_LABELS flag, causing the kernel to silently disable per-file security labeling on both the new and original mounts. This issue was fixed by ensuring the flag is set correctly on reused superblocks during mount option processing.

Impact

The vulnerability causes SELinux to silently disable per-file security labeling on NFSv4 mounts that are mounted multiple times with security_label enabled. This could lead to a loss of mandatory access control enforcement on files accessed via these mounts, potentially weakening the security posture of systems relying on SELinux for fine-grained access control over NFS files.

Summary

The vulnerability occurs in the Linux kernel SELinux code path when an NFSv4 filesystem with security_label is mounted multiple times. The function sget_fc() returns an existing superblock on the second mount, and nfs_get_root() calls security_sb_set_mnt_opts() again. Because the superblock is already marked SB_INITIALIZED, selinux_set_mnt_opts() exits early without setting the SECURITY_LSM_NATIVE_LABELS flag in the kernel flags. Consequently, NFS_CAP_SECURITY_LABEL is cleared on the shared nfs_server, disabling per-file labeling for both mounts. The issue was addressed by modifying the code to set SECURITY_LSM_NATIVE_LABELS on early exits when the superblock is already initialized and uses SECURITY_FS_USE_NATIVE, ensuring consistent security labeling behavior.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 09:59 UTC

Technical details

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