{"id":"CVE-2026-64027","state":"PUBLISHED","title":"net: shaper: rework the VALID marking (again)","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: shaper: rework the VALID marking (again)\n\nRecent commit changed the semantics from NOT_VALID to VALID.\nI didn't realize that the flags are not stored atomically\nwith the entry in XArray. There's still a race of reader\nobserving a VALID mark for a slot, getting interrupted,\nwriter replacing the entry with a different one, reader\ncontinuing, fetching the entry which is now a different\npointer than the pointer for which VALID was meant.\n\nThe biggest consequence of this is that we may see a UAF\nsince net_shaper_rollback() assumed that entries without\nVALID can be freed without observing RCU.\n\nLooks like the XArray marks are buying us nothing at this\npoint. Let's convert the code to an explicit valid field.\nThe smp_load_acquire() / smp_store_release() barriers are\nmarginally cleaner.","publishedAt":"2026-07-19T15:39:18.470Z","updatedAt":"2026-10-19T20:28:09.258Z","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":"93954b40f6a4fc43226c01a15b02732f884500f1","status":"affected","lessThan":"2417df5e7bb4184b9d3a2988036bf2c46e594545","versionType":"git"},{"version":"93954b40f6a4fc43226c01a15b02732f884500f1","status":"affected","lessThan":"96ea960dd40fd55302e0fd755176f26a95e6a50c","versionType":"git"},{"version":"93954b40f6a4fc43226c01a15b02732f884500f1","status":"affected","lessThan":"b8d7519352ba8c6df83259295d4a3bad093cae90","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/net_shaper.h","net/shaper/shaper.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.13","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/net_shaper.h","net/shaper/shaper.c"]}],"references":["https://git.kernel.org/stable/c/2417df5e7bb4184b9d3a2988036bf2c46e594545","https://git.kernel.org/stable/c/96ea960dd40fd55302e0fd755176f26a95e6a50c","https://git.kernel.org/stable/c/b8d7519352ba8c6df83259295d4a3bad093cae90"],"weaknesses":["CWE-362"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64027.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64027","state":"PUBLISHED","datePublished":"2026-07-19T15:39:18.470Z","dateUpdated":"2026-10-19T20:28:09.258Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.028Z"},"containers":{"cna":{"title":"net: shaper: rework the VALID marking (again)","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: shaper: rework the VALID marking (again)\n\nRecent commit changed the semantics from NOT_VALID to VALID.\nI didn't realize that the flags are not stored atomically\nwith the entry in XArray. There's still a race of reader\nobserving a VALID mark for a slot, getting interrupted,\nwriter replacing the entry with a different one, reader\ncontinuing, fetching the entry which is now a different\npointer than the pointer for which VALID was meant.\n\nThe biggest consequence of this is that we may see a UAF\nsince net_shaper_rollback() assumed that entries without\nVALID can be freed without observing RCU.\n\nLooks like the XArray marks are buying us nothing at this\npoint. Let's convert the code to an explicit valid field.\nThe smp_load_acquire() / smp_store_release() barriers are\nmarginally cleaner."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"93954b40f6a4fc43226c01a15b02732f884500f1","status":"affected","lessThan":"2417df5e7bb4184b9d3a2988036bf2c46e594545","versionType":"git"},{"version":"93954b40f6a4fc43226c01a15b02732f884500f1","status":"affected","lessThan":"96ea960dd40fd55302e0fd755176f26a95e6a50c","versionType":"git"},{"version":"93954b40f6a4fc43226c01a15b02732f884500f1","status":"affected","lessThan":"b8d7519352ba8c6df83259295d4a3bad093cae90","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/net_shaper.h","net/shaper/shaper.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.13","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/net_shaper.h","net/shaper/shaper.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/2417df5e7bb4184b9d3a2988036bf2c46e594545"},{"url":"https://git.kernel.org/stable/c/96ea960dd40fd55302e0fd755176f26a95e6a50c"},{"url":"https://git.kernel.org/stable/c/b8d7519352ba8c6df83259295d4a3bad093cae90"}],"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 vulnerability is reached only through the net-shaper generic netlink API (socket syscall), not via remote packet handling. This matches the kernel guidance for tc/netlink-style configuration subsystems.\nAC:L - The family sets parallel_ops, so an attacker can run concurrent SET/GROUP/DELETE and GET/dump requests to control both sides of the TOCTOU race. No attacker-uncontrollable memory layout or rare timing is required beyond issuing concurrent netlink operations.\nPR:L - Exploitation requires triggering net_shaper_rollback() via SET, GROUP, or DELETE, which are gated by GENL_ADMIN_PERM (CAP_NET_ADMIN). That capability is available to an unprivileged user inside a user network namespace, not only to init-namespace root.\nUI:N - Exploitation is fully programmatic through netlink messages and requires no victim interaction such as mounting a filesystem or opening a file.\nS:U - Impact is kernel heap corruption and privilege escalation within the same kernel; it does not cross a VM, container runtime, or IOMMU security boundary by itself.\nC:H - The commit explicitly identifies a use-after-free; concurrent RCU readers can dereference freed net_shaper objects, enabling arbitrary kernel memory disclosure via UAF exploitation.\nI:H - UAF on heap-allocated net_shaper structures can be leveraged for heap grooming and arbitrary write or control-flow hijack, consistent with standard kernel UAF impact.\nA:H - The UAF can cause kernel oops or panic on freed-object access during lookup, dump, or rollback, and matches kernel guidance that any UAF warrants High availability impact."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:38:22.063Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13","versionEndExcluding":"6.18.34"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13","versionEndExcluding":"7.0.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-64027","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:35:31.868695Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-362","lang":"en","type":"CWE","description":"CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:28:09.258Z"}}]}}}