{"id":"CVE-2026-31403","state":"PUBLISHED","title":"NFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd\n\nThe /proc/fs/nfs/exports proc entry is created at module init\nand persists for the module's lifetime. exports_proc_open()\ncaptures the caller's current network namespace and stores\nits svc_export_cache in seq->private, but takes no reference\non the namespace. If the namespace is subsequently torn down\n(e.g. container destruction after the opener does setns() to a\ndifferent namespace), nfsd_net_exit() calls nfsd_export_shutdown()\nwhich frees the cache. Subsequent reads on the still-open fd\ndereference the freed cache_detail, walking a freed hash table.\n\nHold a reference on the struct net for the lifetime of the open\nfile descriptor. This prevents nfsd_net_exit() from running --\nand thus prevents nfsd_export_shutdown() from freeing the cache\n-- while any exports fd is open. cache_detail already stores\nits net pointer (cd->net, set by cache_create_net()), so\nexports_release() can retrieve it without additional per-file\nstorage.","publishedAt":"2026-04-03T15:16:06.444Z","updatedAt":"2026-10-19T18:35:46.952Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"76740c28050dc6db2f5550f1325b00a11bbb3255","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"c7f406fb341d6747634b8b1fa5461656e5e56076","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"d1a19217995df9c7e4118f5a2820c5032fef2945","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"e3d77f935639e6ae4b381c80464c31df998d61f4","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"6a8d70e2ad6aad2c345a5048edcb8168036f97d6","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"e7fcf179b82d3a3730fd8615da01b087cc654d0b","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfsctl.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.9","versionType":"semver"},{"version":"5.10.253","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"6.1.167","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.20","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.10","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfsctl.c"]}],"references":["https://git.kernel.org/stable/c/76740c28050dc6db2f5550f1325b00a11bbb3255","https://git.kernel.org/stable/c/c7f406fb341d6747634b8b1fa5461656e5e56076","https://git.kernel.org/stable/c/d1a19217995df9c7e4118f5a2820c5032fef2945","https://git.kernel.org/stable/c/e3d77f935639e6ae4b381c80464c31df998d61f4","https://git.kernel.org/stable/c/db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6","https://git.kernel.org/stable/c/6a8d70e2ad6aad2c345a5048edcb8168036f97d6","https://git.kernel.org/stable/c/e7fcf179b82d3a3730fd8615da01b087cc654d0b","https://cert-portal.siemens.com/productcert/html/ssa-082556.html","https://cert-portal.siemens.com/productcert/html/ssa-019113.html","https://cert-portal.siemens.com/productcert/html/ssa-457936.html"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/31xxx/CVE-2026-31403.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31403","state":"PUBLISHED","datePublished":"2026-04-03T15:16:06.444Z","dateUpdated":"2026-10-19T18:35:46.952Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-03-09T15:48:24.086Z"},"containers":{"cna":{"title":"NFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd\n\nThe /proc/fs/nfs/exports proc entry is created at module init\nand persists for the module's lifetime. exports_proc_open()\ncaptures the caller's current network namespace and stores\nits svc_export_cache in seq->private, but takes no reference\non the namespace. If the namespace is subsequently torn down\n(e.g. container destruction after the opener does setns() to a\ndifferent namespace), nfsd_net_exit() calls nfsd_export_shutdown()\nwhich frees the cache. Subsequent reads on the still-open fd\ndereference the freed cache_detail, walking a freed hash table.\n\nHold a reference on the struct net for the lifetime of the open\nfile descriptor. This prevents nfsd_net_exit() from running --\nand thus prevents nfsd_export_shutdown() from freeing the cache\n-- while any exports fd is open. cache_detail already stores\nits net pointer (cd->net, set by cache_create_net()), so\nexports_release() can retrieve it without additional per-file\nstorage."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"76740c28050dc6db2f5550f1325b00a11bbb3255","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"c7f406fb341d6747634b8b1fa5461656e5e56076","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"d1a19217995df9c7e4118f5a2820c5032fef2945","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"e3d77f935639e6ae4b381c80464c31df998d61f4","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"6a8d70e2ad6aad2c345a5048edcb8168036f97d6","versionType":"git"},{"version":"96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5","status":"affected","lessThan":"e7fcf179b82d3a3730fd8615da01b087cc654d0b","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfsctl.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.9","versionType":"semver"},{"version":"5.10.253","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"6.1.167","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.20","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.10","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfsctl.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/76740c28050dc6db2f5550f1325b00a11bbb3255"},{"url":"https://git.kernel.org/stable/c/c7f406fb341d6747634b8b1fa5461656e5e56076"},{"url":"https://git.kernel.org/stable/c/d1a19217995df9c7e4118f5a2820c5032fef2945"},{"url":"https://git.kernel.org/stable/c/e3d77f935639e6ae4b381c80464c31df998d61f4"},{"url":"https://git.kernel.org/stable/c/db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6"},{"url":"https://git.kernel.org/stable/c/6a8d70e2ad6aad2c345a5048edcb8168036f97d6"},{"url":"https://git.kernel.org/stable/c/e7fcf179b82d3a3730fd8615da01b087cc654d0b"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable path is reached by locally opening and reading `/proc/fs/nfs/exports`; remote NFS protocol traffic does not invoke this proc seq_file path.\nAC:L - The attacker controls the needed sequence: open the proc file in a network namespace, let that namespace be torn down, then read the still-open fd. No uncontrollable race or special timing is required.\nPR:L - The proc entry is world-readable, and a basic unprivileged local user can plausibly create a temporary network namespace via user namespaces to trigger the lifetime bug. It does not require real root in the initial namespace or NFSD administrator privileges.\nUI:N - No victim action is required; the attacker can open, transfer or retain, and read the file descriptor themselves.\nS:U - The impact remains within the kernel and its local host security authority. This is not a VM escape, IOMMU bypass, or other cross-scope boundary violation.\nC:H - This is a use-after-free of `cache_detail` and its freed hash table during seq_file iteration. The dangling heap objects can be reused and dereferenced, making high confidentiality impact defensible.\nI:H - As a kernel heap use-after-free, reused object contents can potentially be shaped into memory corruption or control-flow primitives. Following the higher-severity rule for UAFs, integrity impact is High.\nA:H - Reading the stale fd dereferences freed kernel memory and can oops or panic the kernel. 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