{ "schema_version": "1.6.1", "id": "RPI-CVE-2025-37984", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2025-37984" ], "published": "2025-05-20T17:07:46Z", "summary": "crypto: ecdsa - Harden against integer overflows in DIV_ROUND_UP()", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncrypto: ecdsa - Harden against integer overflows in DIV_ROUND_UP()\n\nHerbert notes that DIV_ROUND_UP() may overflow unnecessarily if an ecdsa\nimplementation's ->key_size() callback returns an unusually large value.\nHerbert instead suggests (for a division by 8):\n\n X / 8 + !!(X & 7)\n\nBased on this formula, introduce a generic DIV_ROUND_UP_POW2() macro and\nuse it in lieu of DIV_ROUND_UP() for ->key_size() return values.\n\nAdditionally, use the macro in ecc_digits_from_bytes(), whose \"nbytes\"\nparameter is a ->key_size() return value in some instances, or a\nuser-specified ASN.1 length in the case of ecdsa_get_signature_rs().", "severity": [ { "type": 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(strak rule)", "upstream_fixed": "6.12.39" }, "1:6.12.19-1+rpt1": { "linux_commit": "121c2c384b9c2f4790ffb31b2cd25c7d75c8fda0", "upstream_version": "6.12.19", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.39" }, "1:6.12.20-1+rpt1": { "linux_commit": "cd231d4775b14f228606c09f219b48308f6ab3aa", "upstream_version": "6.12.20", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.39" }, "1:6.12.25-1+rpt1+trixie": { "linux_commit": "3dd2c2c507c271d411fab2e82a2b3b7e0b6d3f16", "upstream_version": "6.12.25", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.39" }, "1:6.12.34-1+rpt1": { "linux_commit": "8f77e03530f65209a377d25023e912b288e039cd", "upstream_version": "6.12.34", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.39" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2025-37984" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/f02f0218be412cff1c844addf58e002071be298b" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/f2133b849ff273abddb6da622daddd8f6f6fa448" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/921b8167f10708e38080f84e195cdc68a7a561f1" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/b16510a530d1e6ab9683f04f8fb34f2e0f538275" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T12:19:11Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.0, "cvss_v3_severity": "High", "scenario": "AV:L - The affected code is the in-kernel ECDSA signature-verification path, entered from userspace via `add_key(\"asymmetric\", ...)`/`keyctl(KEYCTL_PKEY_VERIFY)` or local X.509/PKCS#7 verification. No in-kernel network consumer (ksmbd, nfsd, TLS, Bluetooth) performs ECDSA certificate verification, so the flaw is only reachable through local syscalls.\nAC:H - The `DIV_ROUND_UP()` wrap requires a value above `UINT_MAX - 7`, but every in-tree caller bounds its input \u2014 `ecdsa_get_signature_rs()` rejects `vlen > ndigits*8 + 1`, the ASN.1 decoder caps `vlen` at the buffer length, and `ecdsa_key_size()` is fixed at \u226466 bytes by the curve's `nbits`. Triggering it depends on an ECDSA implementation whose `->key_size()` callback reports an ~4 GB key, a precondition entirely outside the attacker's control and absent from any standard configuration.\nPR:L - The verification path is reachable by any unprivileged local user, who may add a crafted self-signed X.509 certificate to their own session keyring and then submit arbitrary signature blobs via `KEYCTL_PKEY_VERIFY`; no capability or namespace privilege is required.\nUI:N - The attacker drives the entire sequence through its own `add_key`/`keyctl` syscalls with attacker-supplied key and signature data; no victim action or cooperating process is needed.\nS:U - The resulting corruption is confined to kernel memory within the same kernel that runs the flawed code; no VM, hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - An underflowed `ndigits` sends `ecc_swap_digits()` iterating up to `0xFFFFFFFF` digits, reading and writing far outside the `ecdsa_raw_sig`/`pub_key` buffers, and the converted digits feed back into signature verification \u2014 an unbounded out-of-bounds access that could expose adjacent kernel memory.\nI:H - `out[--ndigits]` with `ndigits` wrapping to `0xFFFFFFFF` is a wild store roughly 32 GB past the destination buffer, followed by a multi-billion-iteration out-of-bounds write loop \u2014 an out-of-bounds write primitive that scores High.\nA:H - The runaway `ecc_swap_digits()` loop writes over arbitrary kernel memory and will immediately fault or panic the machine, and the corrupted crypto state renders the affected path unusable." } } }