{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23316","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-01-13T15:37:45.995Z","datePublished":"2026-03-25T10:27:11.028Z","dateUpdated":"2026-05-11T22:04:31.681Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-05-11T22:04:31.681Z"},"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."}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/ip_fib.h","net/ipv4/sysctl_net_ipv4.c"],"versions":[{"version":"4ee2a8cace3fb9a34aea6a56426f89d26dd514f3","lessThan":"4bdc94d45d5459f0149085dfc1efe733c8e14f11","status":"affected","versionType":"git"},{"version":"4ee2a8cace3fb9a34aea6a56426f89d26dd514f3","lessThan":"7e4ad34a8889a6a9e0f6cc7c55d02161fe31a199","status":"affected","versionType":"git"},{"version":"4ee2a8cace3fb9a34aea6a56426f89d26dd514f3","lessThan":"607e923a3c1b2120de430b3dcde25ed8ad213c0a","status":"affected","versionType":"git"},{"version":"4ee2a8cace3fb9a34aea6a56426f89d26dd514f3","lessThan":"4ee7fa6cf78ff26d783d39e2949d14c4c1cd5e7f","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/ip_fib.h","net/ipv4/sysctl_net_ipv4.c"],"versions":[{"version":"6.11","status":"affected"},{"version":"0","lessThan":"6.11","status":"unaffected","versionType":"semver"},{"version":"6.12.77","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.17","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"6.19.7","lessThanOrEqual":"6.19.*","status":"unaffected","versionType":"semver"},{"version":"7.0","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.12.77"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.18.17"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.19.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"7.0"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/4bdc94d45d5459f0149085dfc1efe733c8e14f11"},{"url":"https://git.kernel.org/stable/c/7e4ad34a8889a6a9e0f6cc7c55d02161fe31a199"},{"url":"https://git.kernel.org/stable/c/607e923a3c1b2120de430b3dcde25ed8ad213c0a"},{"url":"https://git.kernel.org/stable/c/4ee7fa6cf78ff26d783d39e2949d14c4c1cd5e7f"}],"title":"net: ipv4: fix ARM64 alignment fault in multipath hash seed","x_generator":{"engine":"bippy-1.2.0"}}}}