CVE-2026-99052: selinux: preserve NATIVE_LABELS on already-initialized sb in set_mnt_opts
In the Linux kernel, the following vulnerability has been resolved:
selinux: preserve NATIVELABELS on already-initialized sb in setmntopts
When an NFSv4 filesystem exported with securitylabel is mounted a second time, sgetfc() returns the existing superblock and nfsgetroot() calls securitysbsetmntopts() again on it. Since the superblock is already SBINITIALIZED, selinuxsetmntopts() takes an early exit without setting SECURITYLSMNATIVELABELS in setkernflags. nfsgetroot() then sees kflags without SECURITYLSMNATIVELABELS set and clears NFSCAPSECURITYLABEL on the shared nfsserver, silently disabling per-file labeling for both the new and the original mount.
Commit 3815a245b501 ("security/selinux: fix SECURITYLSMNATIVELABELS on reused superblock") fixed the same problem in selinuxsbclonemntopts(). The reused-superblock path for a plain second mount now goes through sbsetmntopts rather than sbclonemntopts, so it needs the same treatment: on both SESBINITIALIZED early exits, set SECURITYLSMNATIVELABELS in setkernflags when the superblock was already using SECURITYFSUSENATVE.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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azurelinux/kernelto a version that resolves this vulnerability.Fixed in 6.6.161.1-1 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1073.81 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 6.8.0-1068.72 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.3.0-1004.4 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 7.3.0-1004.4 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.3.0-10.10.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-43.43 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1017.18 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1020.21 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1019.19 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1017.19 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1010.11 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1018.18 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1018.18 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 7.0.0-1023.23 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-43.43.1
Event History
Frequently Asked Questions
Which systems are exposed to this issue?
Systems using SELinux with an NFSv4 filesystem exported with security_label are affected when that filesystem is mounted a second time and the existing superblock is reused. The impact is that per-file labeling can be silently disabled on both the new mount and the original mount.
What condition triggers the labeling failure?
The failure occurs on a plain second mount when sget_fc() returns an already-initialized superblock. The SELinux mount-option path exits early without preserving the SECURITY_LSM_NATIVE_LABELS kernel flag, causing NFS_CAP_SECURITY_LABEL to be cleared on the shared NFS server.
How can I tell whether this issue has affected a mount?
The described observable condition is that per-file labeling is disabled for both mounts after a second mount of the same NFSv4 security_label export reuses the superblock. The provided data does not specify a command, log message, or other direct detection method.