{"id":"CVE-2026-74590","state":"PUBLISHED","title":"fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfsverity: Fix bpf_get_fsverity_digest() dynptr assumptions\n\nThe BPF verifier and the dynptr abstraction ensure that the memory space\nreferenced by a dynptr remains valid.  They do not, however, provide any\nguarantee that the contents of the memory are stable.  kfuncs are\nexpected to remain memory-safe even if concurrent modifications occur.\n\nbpf_get_fsverity_digest() didn't follow that: it could crash if\narg->digest_size was concurrently modified.\n\nFix that by using the known-good value hash_alg->digest_size instead.\n\nAlso widen 'dynptr_sz' and 'out_digest_sz' to u64 to match the return\ntype of __bpf_dynptr_size().  It doesn't appear that it can actually be\nmore than INT_MAX currently (since __bpf_dynptr_data_rw() excludes\nfile-based pointers), but the correct type might as well be used.","publishedAt":"2026-08-22T15:31:41.929Z","updatedAt":"2026-10-16T19:05:59.372Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"67814c00de3161181cddd06c77aeaf86ac4cc584","status":"affected","lessThan":"1344b632cb5043e32939a84568125719111c5af3","versionType":"git"},{"version":"67814c00de3161181cddd06c77aeaf86ac4cc584","status":"affected","lessThan":"2a5cfcad1d56e26d645b7887b0ed24c371851525","versionType":"git"},{"version":"67814c00de3161181cddd06c77aeaf86ac4cc584","status":"affected","lessThan":"5bd63cad9df4328a184c409fbdad4f17944bcdb8","versionType":"git"},{"version":"67814c00de3161181cddd06c77aeaf86ac4cc584","status":"affected","lessThan":"3e8ec7c0387273329374f5c7bd61f5f38af71fe1","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/verity/measure.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.8","versionType":"semver"},{"version":"6.12.104","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.45","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.9","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/verity/measure.c"]}],"references":["https://git.kernel.org/stable/c/1344b632cb5043e32939a84568125719111c5af3","https://git.kernel.org/stable/c/2a5cfcad1d56e26d645b7887b0ed24c371851525","https://git.kernel.org/stable/c/5bd63cad9df4328a184c409fbdad4f17944bcdb8","https://git.kernel.org/stable/c/3e8ec7c0387273329374f5c7bd61f5f38af71fe1"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74590.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74590","state":"PUBLISHED","datePublished":"2026-08-22T15:31:41.929Z","dateUpdated":"2026-10-16T19:05:59.372Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.918Z"},"containers":{"cna":{"title":"fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nfsverity: Fix bpf_get_fsverity_digest() dynptr assumptions\n\nThe BPF verifier and the dynptr abstraction ensure that the memory space\nreferenced by a dynptr remains valid.  They do not, however, provide any\nguarantee that the contents of the memory are stable.  kfuncs are\nexpected to remain memory-safe even if concurrent modifications occur.\n\nbpf_get_fsverity_digest() didn't follow that: it could crash if\narg->digest_size was concurrently modified.\n\nFix that by using the known-good value hash_alg->digest_size instead.\n\nAlso widen 'dynptr_sz' and 'out_digest_sz' to u64 to match the return\ntype of __bpf_dynptr_size().  It doesn't appear that it can actually be\nmore than INT_MAX currently (since __bpf_dynptr_data_rw() excludes\nfile-based pointers), but the correct type might as well be used."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"67814c00de3161181cddd06c77aeaf86ac4cc584","status":"affected","lessThan":"1344b632cb5043e32939a84568125719111c5af3","versionType":"git"},{"version":"67814c00de3161181cddd06c77aeaf86ac4cc584","status":"affected","lessThan":"2a5cfcad1d56e26d645b7887b0ed24c371851525","versionType":"git"},{"version":"67814c00de3161181cddd06c77aeaf86ac4cc584","status":"affected","lessThan":"5bd63cad9df4328a184c409fbdad4f17944bcdb8","versionType":"git"},{"version":"67814c00de3161181cddd06c77aeaf86ac4cc584","status":"affected","lessThan":"3e8ec7c0387273329374f5c7bd61f5f38af71fe1","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/verity/measure.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.8","versionType":"semver"},{"version":"6.12.104","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.45","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.9","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/verity/measure.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/1344b632cb5043e32939a84568125719111c5af3"},{"url":"https://git.kernel.org/stable/c/2a5cfcad1d56e26d645b7887b0ed24c371851525"},{"url":"https://git.kernel.org/stable/c/5bd63cad9df4328a184c409fbdad4f17944bcdb8"},{"url":"https://git.kernel.org/stable/c/3e8ec7c0387273329374f5c7bd61f5f38af71fe1"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is only reachable via bpf_get_fsverity_digest(), a BPF kfunc callable from BPF LSM programs loaded through the bpf(2) syscall and triggered by local LSM hooks such as file_open, not by any network-facing kernel service.\nAC:L - Exploitation requires racing concurrent writes to the dynptr-backed fsverity_digest buffer (e.g., bpf_map_update_elem from a sibling thread) against the kfunc's memset; the attacker controls both sides of this race and can repeat it until the bad offset is hit.\nPR:L - Loading and attaching the required BPF LSM program needs CAP_BPF and CAP_PERFMON, which an unprivileged user can obtain as root inside a user namespace (unshare -Ur) without init-namespace privileges, matching kernel CNA guidance for BPF reachability.\nUI:N - No victim interaction is required; the attacker can load the LSM program, prepare a shared dynptr buffer, enable fsverity on a file they own, and trigger file_open themselves to invoke the vulnerable kfunc.\nS:U - Successful exploitation corrupts kernel heap memory and can yield local privilege escalation within the same kernel/host security boundary; it does not by itself cross a guest-to-host, sandbox, or IOMMU isolation boundary.\nC:H - Concurrent tampering with digest_size lets memset() use an attacker-chosen offset beyond the dynptr allocation, causing out-of-bounds kernel heap writes that can corrupt adjacent objects and be leveraged for arbitrary kernel memory disclosure.\nI:H - The faulty memset() can write large zeroed regions far outside the dynptr buffer, giving a controllable out-of-bounds heap write primitive that is exploitable for control-flow hijacking and arbitrary kernel code execution.\nA:H - An out-of-bounds heap write from kernel context can immediately oops/panic the kernel or destabilize critical structures, and the underlying memory corruption reliably threatens system availability even before full exploitation."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-25T05:40:17.568Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"6.12.104"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"6.18.45"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"7.1.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-74590","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T19:01:35.901397Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T19:05:59.372Z"}}]}}}