SignXML's signature verification with HMAC is vulnerable to an algorithm confusion attack

{
  "id": "3637a62235fc39a7bebba791f4c394b79b594536e33a12dcc17de7a5afe874ae",
  "url": "https://osv.dev/vulnerability/CVE-2025-48994",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "SignXML's signature verification with HMAC is vulnerable to an algorithm confusion attack",
    "summary": "SignXML is an implementation of the W3C XML Signature standard in Python. When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (`signxml.XMLVerifier.verify(require_x509=False, hmac_key=...`), versions of SignXML prior to 4.0.4 are vulnerable to a potential algorithm confusion attack. Unless the user explicitly limits the expected signature algorithms using the `signxml.XMLVerifier.verify(expect_config=...)` setting, an attacker may supply a signature unexpectedly signed with a key other than the provided HMAC key, using a different (asymmetric key) signature algorithm. Starting with SignXML 4.0.4, specifying `hmac_key` causes the set of accepted signature algorithms to be restricted to HMAC only, if not already restricted by the user.",
    "evidence": "osv:CVE-2025-48994",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2025-48994",
      "aliases": [
        "CVE-2025-48994",
        "GHSA-6vx8-pcwv-xhf4",
        "PYSEC-2026-1921"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/xml-security/signxml",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "f7da15cbcba2f9f17d4aede3ec83ff165535c4bb"
                },
                {
                  "fixed": "e3c0c2b82a3329a65d917830657649c98b8c7600"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "4.0.4"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "e3c0c2b82a3329a65d917830657649c98b8c7600"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v4.0.3",
            "v4.0.2",
            "v4.0.1",
            "v4.0.0",
            "v3.2.2",
            "v3.2.1",
            "v3.2.0",
            "v3.1.1",
            "v3.1.0",
            "v3.0.2",
            "v3.0.1",
            "v3.0.0",
            "v2.10.1",
            "v2.10.0",
            "v2.9.0",
            "v2.8.2",
            "v2.8.1",
            "v2.8.0",
            "v2.7.3",
            "v2.7.2",
            "v2.7.1",
            "v2.7.0",
            "v2.6.0",
            "v2.5.2",
            "v2.5.1",
            "v2.5.0",
            "v2.4.0",
            "v2.3.0",
            "v2.2.6",
            "v2.2.5",
            "v2.2.4",
            "v2.2.3",
            "v2.2.2",
            "v2.2.1",
            "v2.2.0",
            "v2.1.4",
            "v2.1.3",
            "v2.1.2",
            "v2.1.1",
            "v2.1.0",
            "v2.0.0",
            "v1.0.2",
            "v1.0.1",
            "v1.0.0",
            "v0.6.0",
            "v0.5.0",
            "v0.4.6",
            "v0.4.5",
            "v0.4.4",
            "v0.4.2",
            "v0.4.1",
            "v0.4.0",
            "v0.3.9",
            "v0.3.8",
            "v0.3.7",
            "v0.3.6",
            "v0.3.5",
            "v0.3.4",
            "v0.3.3",
            "v0.3.2",
            "v0.3.1",
            "v0.3.0",
            "v0.2.8",
            "v0.2.7",
            "v0.2.6",
            "v0.2.5",
            "v0.2.4",
            "v0.2.3",
            "v0.2.2",
            "v0.2.0",
            "v0.1.9",
            "v0.1.8",
            "v0.1.7",
            "v0.1.6",
            "v0.1.5",
            "v0.1.4",
            "v0.1.3",
            "v0.1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-48994.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:36.805691917Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/48xxx/CVE-2025-48994.json",
        "https://github.com/XML-Security/signxml/security/advisories/GHSA-6vx8-pcwv-xhf4",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-48994",
        "https://github.com/XML-Security/signxml/commit/e3c0c2b82a3329a65d917830657649c98b8c7600"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-303"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/48xxx/CVE-2025-48994.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-48994",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504222,
  "published_at": "2025-06-02T16:22:08.966+00:00"
}