{
    "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"
            }
        }
    }
}