CVE-2026-23316

{"id": "CVE-2026-23316", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.5, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 1.8}]}, "published": "2026-03-25T11:16:28.063", "references": [{"url": "https://git.kernel.org/stable/c/4bdc94d45d5459f0149085dfc1efe733c8e14f11", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/4ee7fa6cf78ff26d783d39e2949d14c4c1cd5e7f", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/607e923a3c1b2120de430b3dcde25ed8ad213c0a", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/7e4ad34a8889a6a9e0f6cc7c55d02161fe31a199", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Primary", "source": "nvd@nist.gov", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv4: fix ARM64 alignment fault in multipath hash seed\n\n`struct sysctl_fib_multipath_hash_seed` contains two u32 fields\n(user_seed and mp_seed), making it an 8-byte structure with a 4-byte\nalignment requirement.\n\nIn `fib_multipath_hash_from_keys()`, the code evaluates the entire\nstruct atomically via `READ_ONCE()`:\n\n mp_seed = READ_ONCE(net->ipv4.sysctl_fib_multipath_hash_seed).mp_seed;\n\nWhile this silently works on GCC by falling back to unaligned regular\nloads which the ARM64 kernel tolerates, it causes a fatal kernel panic\nwhen compiled with Clang and LTO enabled.\n\nCommit e35123d83ee3 (\"arm64: lto: Strengthen READ_ONCE() to acquire\nwhen CONFIG_LTO=y\") strengthens `READ_ONCE()` to use Load-Acquire\ninstructions (`ldar` / `ldapr`) to prevent compiler reordering bugs\nunder Clang LTO. Since the macro evaluates the full 8-byte struct,\nClang emits a 64-bit `ldar` instruction. ARM64 architecture strictly\nrequires `ldar` to be naturally aligned, thus executing it on a 4-byte\naligned address triggers a strict Alignment Fault (FSC = 0x21).\n\nFix the read side by moving the `READ_ONCE()` directly to the `u32`\nmember, which emits a safe 32-bit `ldar Wn`.\n\nFurthermore, Eric Dumazet pointed out that `WRITE_ONCE()` on the entire\nstruct in `proc_fib_multipath_hash_set_seed()` is also flawed. Analysis\nshows that Clang splits this 8-byte write into two separate 32-bit\n`str` instructions. While this avoids an alignment fault, it destroys\natomicity and exposes a tear-write vulnerability. Fix this by\nexplicitly splitting the write into two 32-bit `WRITE_ONCE()`\noperations.\n\nFinally, add the missing `READ_ONCE()` when reading `user_seed` in\n`proc_fib_multipath_hash_seed()` to ensure proper pairing and\nconcurrency safety."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnet: ipv4: solucionar fallo de alineaci\u00f3n ARM64 en la semilla de hash multipath\n\n'struct sysctl_fib_multipath_hash_seed' contiene dos campos u32 (user_seed y mp_seed), convirti\u00e9ndola en una estructura de 8 bytes con un requisito de alineaci\u00f3n de 4 bytes.\n\nEn 'fib_multipath_hash_from_keys()', el c\u00f3digo eval\u00faa la estructura completa at\u00f3micamente a trav\u00e9s de 'READ_ONCE()':\n\n mp_seed = 'READ_ONCE'(net->ipv4.sysctl_fib_multipath_hash_seed).mp_seed;\n\nAunque esto funciona silenciosamente en GCC al recurrir a cargas regulares no alineadas que el kernel ARM64 tolera, causa un p\u00e1nico fatal del kernel cuando se compila con Clang y LTO habilitado.\n\nEl commit e35123d83ee3 ('arm64: lto: Strengthen 'READ_ONCE()' to acquire when CONFIG_LTO=y') refuerza 'READ_ONCE()' para usar instrucciones Load-Acquire ('ldar' / 'ldapr') para prevenir errores de reordenamiento del compilador bajo Clang LTO. Dado que la macro eval\u00faa la estructura completa de 8 bytes, Clang emite una instrucci\u00f3n 'ldar' de 64 bits. La arquitectura ARM64 requiere estrictamente que 'ldar' est\u00e9 naturalmente alineado, por lo tanto, ejecutarlo en una direcci\u00f3n alineada a 4 bytes desencadena un fallo de alineaci\u00f3n estricto (FSC = 0x21).\n\nSolucionar el lado de lectura moviendo 'READ_ONCE()' directamente al miembro 'u32', lo que emite un 'ldar Wn' seguro de 32 bits.\n\nAdem\u00e1s, Eric Dumazet se\u00f1al\u00f3 que 'WRITE_ONCE()' en la estructura completa en 'proc_fib_multipath_hash_set_seed()' tambi\u00e9n es defectuoso. El an\u00e1lisis muestra que Clang divide esta escritura de 8 bytes en dos instrucciones 'str' separadas de 32 bits. Aunque esto evita un fallo de alineaci\u00f3n, destruye la atomicidad y expone una vulnerabilidad de escritura fragmentada. Solucionar esto dividiendo expl\u00edcitamente la escritura en dos operaciones 'WRITE_ONCE()' de 32 bits.\n\nFinalmente, a\u00f1adir el 'READ_ONCE()' faltante al leer 'user_seed' en 'proc_fib_multipath_hash_seed()' para asegurar un emparejamiento adecuado y seguridad de concurrencia."}], "lastModified": "2026-04-23T21:07:02.380", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "A9108695-408B-4C1A-A58A-9B59404F6DEE", "versionEndExcluding": "6.12.77", "versionStartIncluding": "6.11.1"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "A5E006E4-59C7-43C1-9231-62A72219F2BA", "versionEndExcluding": "6.18.17", "versionStartIncluding": "6.13"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "69245D10-0B71-485E-80C3-A64F077004D3", "versionEndExcluding": "6.19.7", "versionStartIncluding": "6.19"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.11:-:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "4770BA57-3F3F-493B-8608-EC3B25254949"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}], "operator": "OR"}]}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}