Timing side-channel in ML-DSA decomposition

{
  "id": "72b6497f169333f343b1c443c9104677a0c0e86cb74b58d6bcce50aac5e1df6a",
  "url": "https://osv.dev/vulnerability/RUSTSEC-2025-0144",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Timing side-channel in ML-DSA decomposition",
    "summary": "### Summary A timing side-channel was discovered in the Decompose algorithm which is used during ML-DSA signing to generate hints for the signature. ### Details The analysis was performed using a constant-time analyzer that examines compiled assembly code for instructions with data-dependent timing behavior. The analyzer flags: - **UDIV/SDIV instructions**: Hardware division instructions have early termination optimizations where execution time depends on operand values. The `decompose` function used a hardware division instruction to compute `r1.0 / TwoGamma2::U32`. This function is called during signing through `high_bits()` and `low_bits()`, which process values derived from secret key components: - `(&w - &cs2).low_bits()` where `cs2` is derived from secret key component `s2` - `Hint::new()` calls `high_bits()` on values derived from secret key component `t0` **Original Code**: ```rust fn decompose(self) -> (Elem, Elem) { // ... let mut r1 = r_plus - r0; r1.0 /= TwoGamma2::U32; // Variable-time division on secret-derived data (r1, r0) } ``` ### Impact The dividend (`r1.0`) is derived from secret key material. An attacker with precise timing measurements could extract information about the signing key by observing timing variations in the division operation. ### Mitigation Integer division was replaced with a constant-time Barrett reduction.",
    "evidence": "osv:RUSTSEC-2025-0144",
    "products": [
      {
        "name": {
          "value": "ml-dsa",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "0.1.0-rc.3",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "RUSTSEC-2025-0144",
      "aliases": [
        "CVE-2026-22705",
        "GHSA-hcp2-x6j4-29j7",
        "RUSTSEC-2025-0144"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0.0.0-0"
                },
                {
                  "fixed": "0.1.0-rc.3"
                }
              ]
            }
          ],
          "package": {
            "name": "ml-dsa",
            "purl": "pkg:cargo/ml-dsa",
            "ecosystem": "crates.io"
          },
          "database_specific": {
            "cvss": "CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N",
            "source": "https://github.com/rustsec/advisory-db/blob/osv/crates/RUSTSEC-2025-0144.json",
            "categories": [
              "crypto-failure"
            ],
            "informational": null
          },
          "ecosystem_specific": {
            "affects": {
              "os": [],
              "arch": [],
              "functions": []
            },
            "affected_functions": null
          }
        }
      ],
      "modified": "2026-10-12T18:00:13.061349808Z",
      "provider": "osv",
      "references": [
        "https://crates.io/crates/ml-dsa",
        "https://rustsec.org/advisories/RUSTSEC-2025-0144.html",
        "https://github.com/RustCrypto/signatures/pull/1144"
      ],
      "provider_metadata": {
        "license": "CC-BY-4.0"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-22705",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 306437,
  "published_at": "2025-12-12T12:00:00+00:00"
}