{"cve":"CVE-2026-99040","nvd":{"published":"2026-10-23T13:17:27.360","modified":"2026-10-23T13:17:27.360","status":"Received","description":"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_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.","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/11516a0c402a6c1fa52254aa70d8d65fb921e59e","https://git.kernel.org/stable/c/305f1828b871dd46bf41addeb6f11d2c162dcb25","https://git.kernel.org/stable/c/da0b595d8e6e2dd798f6e34e09dc51a13b888514","https://git.kernel.org/stable/c/dd3ea3fcba7c75493760cdbccd35f029597e8d5e","https://git.kernel.org/stable/c/f99399b48e3edd6851fac34cd329bab9f1f33baf"],"products":[],"source":"nvd","synced_at":"2026-10-23T16:39:28.036610720+00:00"},"epss":{"cve":"CVE-2026-99040","score":0.00181,"percentile":0.07629,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}