{"id":"CVE-2026-43403","state":"PUBLISHED","title":"nsfs: tighten permission checks for ns iteration ioctls","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnsfs: tighten permission checks for ns iteration ioctls\n\nEven privileged services should not necessarily be able to see other\nprivileged service's namespaces so they can't leak information to each\nother. Use may_see_all_namespaces() helper that centralizes this policy\nuntil the nstree adapts.","publishedAt":"2026-05-08T14:21:44.204Z","updatedAt":"2026-08-05T12:27:47.212Z","severity":{"score":8.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"a1d220d9dafa8d76ba60a784a1016c3134e6a1e8","status":"affected","lessThan":"3376b345df155ca36d8611857b41ff7d5183fc38","versionType":"git"},{"version":"a1d220d9dafa8d76ba60a784a1016c3134e6a1e8","status":"affected","lessThan":"2f3dea284c761c890d676f77d5e55c0c496b4ef4","versionType":"git"},{"version":"a1d220d9dafa8d76ba60a784a1016c3134e6a1e8","status":"affected","lessThan":"0ad650e60150eda789deca5e78a6a09d26bf8fc9","versionType":"git"},{"version":"a1d220d9dafa8d76ba60a784a1016c3134e6a1e8","status":"affected","lessThan":"e6b899f08066e744f89df16ceb782e06868bd148","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nsfs.c","include/linux/ns_common.h","kernel/nscommon.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.12","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":"6.19.9","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/nsfs.c","include/linux/ns_common.h","kernel/nscommon.c"]}],"references":["https://git.kernel.org/stable/c/3376b345df155ca36d8611857b41ff7d5183fc38","https://git.kernel.org/stable/c/2f3dea284c761c890d676f77d5e55c0c496b4ef4","https://git.kernel.org/stable/c/0ad650e60150eda789deca5e78a6a09d26bf8fc9","https://git.kernel.org/stable/c/e6b899f08066e744f89df16ceb782e06868bd148"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43403.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43403","state":"PUBLISHED","datePublished":"2026-05-08T14:21:44.204Z","dateUpdated":"2026-08-05T12:27:47.212Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:56.007Z"},"containers":{"cna":{"title":"nsfs: tighten permission checks for ns iteration ioctls","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnsfs: tighten permission checks for ns iteration ioctls\n\nEven privileged services should not necessarily be able to see other\nprivileged service's namespaces so they can't leak information to each\nother. Use may_see_all_namespaces() helper that centralizes this policy\nuntil the nstree adapts."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"a1d220d9dafa8d76ba60a784a1016c3134e6a1e8","status":"affected","lessThan":"3376b345df155ca36d8611857b41ff7d5183fc38","versionType":"git"},{"version":"a1d220d9dafa8d76ba60a784a1016c3134e6a1e8","status":"affected","lessThan":"2f3dea284c761c890d676f77d5e55c0c496b4ef4","versionType":"git"},{"version":"a1d220d9dafa8d76ba60a784a1016c3134e6a1e8","status":"affected","lessThan":"0ad650e60150eda789deca5e78a6a09d26bf8fc9","versionType":"git"},{"version":"a1d220d9dafa8d76ba60a784a1016c3134e6a1e8","status":"affected","lessThan":"e6b899f08066e744f89df16ceb782e06868bd148","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nsfs.c","include/linux/ns_common.h","kernel/nscommon.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.12","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":"6.19.9","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/nsfs.c","include/linux/ns_common.h","kernel/nscommon.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/3376b345df155ca36d8611857b41ff7d5183fc38"},{"url":"https://git.kernel.org/stable/c/2f3dea284c761c890d676f77d5e55c0c496b4ef4"},{"url":"https://git.kernel.org/stable/c/0ad650e60150eda789deca5e78a6a09d26bf8fc9"},{"url":"https://git.kernel.org/stable/c/e6b899f08066e744f89df16ceb782e06868bd148"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable path is reached by a local `ioctl()` on an nsfs mount-namespace file descriptor, such as one obtained from `/proc/self/ns/mnt` or pidfd namespace ioctls. There is no network, adjacent, or physical attack path.\nAC:L - Triggering is deterministic: open a mount namespace fd and issue `NS_MNT_GET_NEXT` or `NS_MNT_GET_PREV`. There is no race or special memory-layout condition required.\nPR:L - The pre-fix check only required `CAP_SYS_ADMIN` in the target mount namespace's owning user namespace, which can be satisfied through user namespaces in plausible deployments. Under the higher-severity rule, this is Low rather than High.\nUI:N - No victim interaction is needed once the attacker has local execution and the relevant namespace capability. The attacker directly invokes the ioctl.\nS:C - The bug lets one namespace-confined service obtain file descriptors for other mount namespaces, bypassing the intended namespace visibility boundary. That can cross container or service isolation boundaries.\nC:H - The returned namespace fd and mount namespace id allow enumeration with `listmount()` and `statmount()`, exposing mount topology, paths, sources, options, and related metadata from another namespace. In plausible privileged-container scenarios, the fd can also enable `setns()` into the target mount namespace and expose sensitive filesystem contents.\nI:H - With the leaked mount namespace fd and the same namespace capabilities required by the vulnerable path, an attacker can plausibly `setns()` into another mount namespace and modify writable files or mount state there. This can compromise integrity across the namespace boundary.\nA:H - After obtaining and entering another mount namespace in a privileged scenario, the attacker can disrupt that namespace by altering or unmounting resources or damaging writable files. This can cause high availability impact to the affected service or container."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:27:47.212Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.12.78"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.18.20"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.19.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}