{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-39802","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-04-16T07:20:57.134Z","datePublished":"2025-09-15T12:36:44.792Z","dateUpdated":"2026-08-05T12:05:17.325Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:05:17.325Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nlib/crypto: arm/poly1305: Fix register corruption in no-SIMD contexts\n\nRestore the SIMD usability check that was removed by commit 773426f4771b\n(\"crypto: arm/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 through WireGuard, IPsec ESP (rfc7539esp) and kTLS on 32-bit ARM routers, IoT gateways and automotive units, so an off-path attacker's packets are what cause the vulnerable `poly1305_blocks_arch()` invocation. No local access to the target is required.\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(in_hardirq())`/`BUG_ON(irqs_disabled())` in ARM's `kernel_neon_begin()` fires deterministically, and the attacker only has to keep sending traffic that gets MAC-verified.\nPR:N - For ChaCha20-Poly1305 AEAD the Poly1305 tag computation *is* the authentication step, so it processes an unauthenticated peer's packet before any credential is validated (e.g. WireGuard handshake-initiation and cookie messages accepted from any source address); no account or key on the target is needed.\nUI:N - Packet reception and the resulting AEAD tag verification happen automatically inside the kernel with no action by any local user or administrator.\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 ARM the `BUG_ON` pair in `kernel_neon_begin()` traps before any NEON instruction executes, so the VFP/NEON register leak the check guards against is not reached in the `have_neon` configuration and no kernel 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(in_hardirq())`/`BUG_ON(irqs_disabled())` raises a kernel BUG from interrupt or IRQ-disabled context, producing a fatal exception in interrupt / panic that takes down the whole system, and it can be re-triggered simply by 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/arm/poly1305-glue.c"],"versions":[{"version":"773426f4771bdd82ac5c834bf4c1775315c73a46","lessThan":"87bdfba903be7084cb3ee04032b14a81181fe413","status":"affected","versionType":"git"},{"version":"773426f4771bdd82ac5c834bf4c1775315c73a46","lessThan":"52c3e242f4d0043186b70d65460ba1767f27494a","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/arm/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/87bdfba903be7084cb3ee04032b14a81181fe413"},{"url":"https://git.kernel.org/stable/c/52c3e242f4d0043186b70d65460ba1767f27494a"}],"title":"lib/crypto: arm/poly1305: Fix register corruption in no-SIMD contexts","x_generator":{"engine":"bippy-1.2.0"}}}}