{
    "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"
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    }
}