{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-39804","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-04-16T07:20:57.135Z","datePublished":"2025-09-15T12:36:46.483Z","dateUpdated":"2026-08-05T12:05:18.397Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:05:18.397Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nlib/crypto: arm64/poly1305: Fix register corruption in no-SIMD contexts\n\nRestore the SIMD usability check that was removed by commit a59e5468a921\n(\"crypto: arm64/poly1305 - Add block-only interface\").\n\nThis safety check is cheap and is well worth eliminating a footgun.\nWhile the Poly1305 functions should not be called when SIMD registers\nare unusable, if they are anyway, they should just do the right thing\ninstead of corrupting random tasks' registers and/or computing incorrect\nMACs.  Fixing this is also needed for poly1305_kunit to pass.\n\nJust use may_use_simd() instead of the original crypto_simd_usable(),\nsince poly1305_kunit won't rely on crypto_simd_disabled_for_test."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - Poly1305 is the MAC half of ChaCha20-Poly1305 and is driven directly by remote peer data in WireGuard, IPsec ESP (rfc7539esp) and kTLS on arm64 routers, phones and cloud servers, so an off-path attacker's packets are what cause the vulnerable `poly1305_blocks_arch()` invocation.\nAC:L - There is no race to win and no memory layout to groom; once the MAC computation runs in a context where SIMD is unusable the `BUG_ON(!may_use_simd())` in `kernel_neon_begin()` fires deterministically, and the attacker only has to send traffic that is MAC-verified.\nPR:N - For ChaCha20-Poly1305 AEAD the Poly1305 tag computation is itself the authentication step, so it processes an unauthenticated peer's packet before any credential is validated; no account or key on the target is needed.\nUI:N - Packet reception and the resulting AEAD tag verification happen automatically in the kernel with no action by any local user.\nS:U - The fault and its consequences are entirely within the kernel's own security authority; no VM, IOMMU or sandbox boundary is crossed.\nC:N - On arm64 the `BUG_ON` in `kernel_neon_begin()` traps before any NEON instruction executes, so the FPSIMD-register leak that the check guards against cannot be reached in the `have_neon` configuration and no memory is disclosed.\nI:N - The trap gives the attacker no write primitive, and a Poly1305 tag computed from a disturbed state fails closed on verification rather than allowing forged data to be accepted.\nA:H - Hitting `BUG_ON(!may_use_simd())` raises a kernel BUG from interrupt context, producing a fatal exception in interrupt / panic that takes down the whole system, and it can be re-triggered by simply resending traffic."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["lib/crypto/arm64/poly1305-glue.c"],"versions":[{"version":"a59e5468a921937cb7317892779c67046ad9f5cc","lessThan":"ef74efa598b7bbc5c24509f7f56af2806f81c339","status":"affected","versionType":"git"},{"version":"a59e5468a921937cb7317892779c67046ad9f5cc","lessThan":"eec76ea5a7213c48529a46eed1b343e5cee3aaab","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["lib/crypto/arm64/poly1305-glue.c"],"versions":[{"version":"6.16","status":"affected"},{"version":"0","lessThan":"6.16","status":"unaffected","versionType":"semver"},{"version":"6.16.4","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":"6.16","versionEndExcluding":"6.16.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"6.17"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/ef74efa598b7bbc5c24509f7f56af2806f81c339"},{"url":"https://git.kernel.org/stable/c/eec76ea5a7213c48529a46eed1b343e5cee3aaab"}],"title":"lib/crypto: arm64/poly1305: Fix register corruption in no-SIMD contexts","x_generator":{"engine":"bippy-1.2.0"}}}}