{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-39964","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-04-16T07:20:57.149Z","datePublished":"2025-10-13T13:48:30.334Z","dateUpdated":"2026-08-05T12:06:33.126Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:06:33.126Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ncrypto: af_alg - Disallow concurrent writes in af_alg_sendmsg\n\nIssuing two writes to the same af_alg socket is bogus as the\ndata will be interleaved in an unpredictable fashion.  Furthermore,\nconcurrent writes may create inconsistencies in the internal\nsocket state.\n\nDisallow this by adding a new ctx->write field that indiciates\nexclusive ownership for writing."}],"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 vulnerability is reached through the AF_ALG socket family via `socket()`/`bind()`/`sendmsg()`/`recvmsg()` syscalls, which requires local system access. There is no remote or adjacent-network path to `af_alg_sendmsg()`.\nAC:L - The attacker controls both sides of the race entirely — two of its own threads on a socket it owns — and can force writer A to park deterministically in `af_alg_wait_for_wmem()` by sizing `SO_SNDBUF` and filling it, then wake it on demand with its own `recvmsg()`. The error exit that leaves `cur == 0` is triggered at will with a deliberately faulting user buffer, so no condition is outside the attacker's control.\nPR:L - `alg_create()`, `alg_bind()` and `alg_setkey()` perform no capability checks whatsoever, so any unprivileged local user — including one inside a container or unprivileged user namespace — can open, bind and write to an AF_ALG skcipher/aead socket. The required modules are auto-loaded on demand via `MODULE_ALIAS_NETPROTO(AF_ALG)` and `request_module(\"algif-%s\")`.\nUI:N - The attacking process performs every step itself — socket creation, bind, and the two concurrent `sendmsg()` calls. No victim action or interaction of any kind is needed.\nS:U - The corruption is confined to kernel heap objects (`struct af_alg_tsgl`/scatterlist and adjacent slab memory) within the same security authority. No hypervisor, IOMMU, or other trust boundary is crossed.\nC:H - The out-of-bounds scatterlist entry is fabricated from kernel list pointers and is subsequently handed to the cipher by `skcipher_recvmsg`/`aead_recvmsg` via `af_alg_pull_tsgl()`, so arbitrary kernel memory is encrypted/decrypted and returned to userspace. This yields a kernel memory disclosure primitive, not merely a pointer leak.\nI:H - `memcpy_from_msg(page_address(sg_page(sg)) + sg->offset + sg->length, msg, len)` on the underflowed scatterlist writes attacker-controlled data of attacker-chosen length to an address derived from attacker-influenceable heap contents. Combined with heap grooming of the 4KB tsgl allocations, this is a controlled kernel write suitable for privilege escalation.\nA:H - Dereferencing `page_address(sg_page(sg))` on a bogus page_link, and the later `put_page()` on that fabricated page, reliably produce an oops/panic or page refcount corruption. Any unprivileged user can trigger this repeatedly, crashing the machine."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["crypto/af_alg.c","include/crypto/if_alg.h"],"versions":[{"version":"8ff590903d5fc7f5a0a988c38267a3d08e6393a2","lessThan":"0f28c4adbc4a97437874c9b669fd7958a8c6d6ce","status":"affected","versionType":"git"},{"version":"8ff590903d5fc7f5a0a988c38267a3d08e6393a2","lessThan":"e4c1ec11132ec466f7362a95f36a506ce4dc08c9","status":"affected","versionType":"git"},{"version":"8ff590903d5fc7f5a0a988c38267a3d08e6393a2","lessThan":"1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8","status":"affected","versionType":"git"},{"version":"8ff590903d5fc7f5a0a988c38267a3d08e6393a2","lessThan":"7c4491b5644e3a3708f3dbd7591be0a570135b84","status":"affected","versionType":"git"},{"version":"8ff590903d5fc7f5a0a988c38267a3d08e6393a2","lessThan":"9aee87da5572b3a14075f501752e209801160d3d","status":"affected","versionType":"git"},{"version":"8ff590903d5fc7f5a0a988c38267a3d08e6393a2","lessThan":"45bcf60fe49b37daab1acee57b27211ad1574042","status":"affected","versionType":"git"},{"version":"8ff590903d5fc7f5a0a988c38267a3d08e6393a2","lessThan":"1b34cbbf4f011a121ef7b2d7d6e6920a036d5285","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["crypto/af_alg.c","include/crypto/if_alg.h"],"versions":[{"version":"2.6.38","status":"affected"},{"version":"0","lessThan":"2.6.38","status":"unaffected","versionType":"semver"},{"version":"5.10.245","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.194","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.154","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.108","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.49","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.16.9","lessThanOrEqual":"6.16.*","status":"unaffected","versionType":"semver"},{"version":"6.17","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":"2.6.38","versionEndExcluding":"5.10.245"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"5.15.194"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"6.1.154"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"6.6.108"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"6.12.49"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"6.16.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"6.17"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce"},{"url":"https://git.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9"},{"url":"https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8"},{"url":"https://git.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84"},{"url":"https://git.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d"},{"url":"https://git.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042"},{"url":"https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285"}],"title":"crypto: af_alg - 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