{"id":"CVE-2026-99040","title":"KEYS: Fix add_key() race with keyring restriction","summary":"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->restrict_link before taking\nthe destination keyring's semaphore.  keyring…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c < 305f1828b871dd46bf41addeb6f11d2c162dcb25","Linux >= 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c < f99399b48e3edd6851fac34cd329bab9f1f33baf","Linux >= 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c < 11516a0c402a6c1fa52254aa70d8d65fb921e59e","Linux >= 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c < da0b595d8e6e2dd798f6e34e09dc51a13b888514","Linux >= 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c < dd3ea3fcba7c75493760cdbccd35f029597e8d5e","Linux 4.7"],"published":"2026-10-23","updated":"2026-10-23","sourceUpdated":"2026-10-23T12:21:59.288Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99040","references":[{"url":"https://git.kernel.org/stable/c/305f1828b871dd46bf41addeb6f11d2c162dcb25"},{"url":"https://git.kernel.org/stable/c/f99399b48e3edd6851fac34cd329bab9f1f33baf"},{"url":"https://git.kernel.org/stable/c/11516a0c402a6c1fa52254aa70d8d65fb921e59e"},{"url":"https://git.kernel.org/stable/c/da0b595d8e6e2dd798f6e34e09dc51a13b888514"},{"url":"https://git.kernel.org/stable/c/dd3ea3fcba7c75493760cdbccd35f029597e8d5e"}],"tags":["cve.org"],"ingestedAt":"2026-10-23T13:24:55.529Z","slug":"CVE-2026-99040","body":"## Overview\n\nIn 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->restrict_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->sem.\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.\n\n## Affected\n\n- `Linux >= 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c < 305f1828b871dd46bf41addeb6f11d2c162dcb25`\n- `Linux >= 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c < f99399b48e3edd6851fac34cd329bab9f1f33baf`\n- `Linux >= 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c < 11516a0c402a6c1fa52254aa70d8d65fb921e59e`\n- `Linux >= 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c < da0b595d8e6e2dd798f6e34e09dc51a13b888514`\n- `Linux >= 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c < dd3ea3fcba7c75493760cdbccd35f029597e8d5e`\n- `Linux 4.7`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}