{"id":"CVE-2026-99040","summary":"KEYS: Fix add_key() race with keyring restriction","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nKEYS: Fix add_key() race with keyring restriction\n\n__key_create_or_update() snapshots keyring-\u003erestrict_link before taking\nthe destination keyring's semaphore.  keyring_restrict() installs a\nrestriction while holding that semaphore.\n\nThis allows a writer to observe no restriction, wait for the keyring\nowner to install a reject-all restriction and return successfully, and\nthen link a key using the stale NULL snapshot.  The writer only needs\nwrite permission on the destination keyring.\n\nMove the restrict_link read after __key_link_lock() and\n__key_link_begin().  The read and the subsequent restriction check are\nthen serialized with restriction installation by keyring-\u003esem.\n\nThe race was reproduced on v7.2.8 in 19 executions where restriction\ninstallation returned before the link completed.  All 19 linked the key\ndespite the reject-all restriction.  With this change, 312 executions\nreached the same ordering and every add_key() call failed with -EPERM.\n\nThe issue was found by manual concurrency analysis assisted by AI-based\nanalysis and independently verified with a QEMU reproducer and kernel\ninstrumentation.","modified":"2026-11-01T02:30:27.437823207Z","published":"2026-10-23T12:21:59.288Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/99xxx/CVE-2026-99040.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/11516a0c402a6c1fa52254aa70d8d65fb921e59e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/24806fc9bca28fa1433bf938d1424dcb45d80e50"},{"type":"WEB","url":"https://git.kernel.org/stable/c/305f1828b871dd46bf41addeb6f11d2c162dcb25"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9a5c2700336878465a630804a2d21864f22eca9c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b3e404550dc2b7f3d4bb64b1da8005a1fa9a798d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/da0b595d8e6e2dd798f6e34e09dc51a13b888514"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dd3ea3fcba7c75493760cdbccd35f029597e8d5e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f99399b48e3edd6851fac34cd329bab9f1f33baf"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/99xxx/CVE-2026-99040.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-99040"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c"},{"fixed":"24806fc9bca28fa1433bf938d1424dcb45d80e50"},{"fixed":"9a5c2700336878465a630804a2d21864f22eca9c"},{"fixed":"b3e404550dc2b7f3d4bb64b1da8005a1fa9a798d"},{"fixed":"305f1828b871dd46bf41addeb6f11d2c162dcb25"},{"fixed":"f99399b48e3edd6851fac34cd329bab9f1f33baf"},{"fixed":"11516a0c402a6c1fa52254aa70d8d65fb921e59e"},{"fixed":"da0b595d8e6e2dd798f6e34e09dc51a13b888514"},{"fixed":"dd3ea3fcba7c75493760cdbccd35f029597e8d5e"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-99040.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.7.0"},{"fixed":"5.10.273"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.224"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.191"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.160"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.113"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.57"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.11"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-99040.json"}}],"schema_version":"1.9.2"}