PYSEC-2026-1921

Vulnerability from pysec - Published: 2026-07-07 16:02 - Updated: 2026-07-07 17:25
VLAI
Details

When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), prior versions of SignXML 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.

Severity
6.9 (Medium)
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
Impacted products
Name purl
signxml pkg:pypi/signxml
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "signxml",
        "purl": "pkg:pypi/signxml"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.0.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.0.1",
        "0.1.0",
        "0.1.1",
        "0.1.2",
        "0.1.3",
        "0.1.4",
        "0.1.5",
        "0.1.6",
        "0.1.7",
        "0.1.8",
        "0.1.9",
        "0.2.0",
        "0.2.1",
        "0.2.2",
        "0.2.3",
        "0.2.4",
        "0.2.5",
        "0.2.6",
        "0.2.7",
        "0.2.8",
        "0.2.9",
        "0.3.0",
        "0.3.1",
        "0.3.2",
        "0.3.3",
        "0.3.4",
        "0.3.5",
        "0.3.6",
        "0.3.7",
        "0.3.8",
        "0.3.9",
        "0.4.0",
        "0.4.1",
        "0.4.2",
        "0.4.3",
        "0.4.4",
        "0.4.5",
        "0.4.6",
        "0.5.0",
        "0.6.0",
        "1.0.0",
        "1.0.1",
        "1.0.2",
        "2.0.0",
        "2.1.4",
        "2.10.0",
        "2.10.1",
        "2.2.0",
        "2.2.1",
        "2.2.2",
        "2.2.3",
        "2.2.4",
        "2.2.6",
        "2.3.0",
        "2.4.0",
        "2.5.2",
        "2.6.0",
        "2.7.0",
        "2.7.1",
        "2.7.2",
        "2.7.3",
        "2.8.0",
        "2.8.1",
        "2.8.2",
        "2.9.0",
        "3.0.0",
        "3.0.1",
        "3.0.2",
        "3.1.0",
        "3.1.1",
        "3.2.0",
        "3.2.1",
        "3.2.2",
        "4.0.0",
        "4.0.1",
        "4.0.2",
        "4.0.3"
      ]
    }
  ],
  "aliases": [
    "CVE-2025-48994",
    "GHSA-6vx8-pcwv-xhf4"
  ],
  "details": "When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (`signxml.XMLVerifier.verify(require_x509=False, hmac_key=...`), prior versions of SignXML 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.\n\nStarting 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.",
  "id": "PYSEC-2026-1921",
  "modified": "2026-07-07T17:25:23.925481Z",
  "published": "2026-07-07T16:02:53.867049Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/XML-Security/signxml/security/advisories/GHSA-6vx8-pcwv-xhf4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-48994"
    },
    {
      "type": "WEB",
      "url": "https://github.com/XML-Security/signxml/commit/e3c0c2b82a3329a65d917830657649c98b8c7600"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/XML-Security/signxml"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/signxml"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-6vx8-pcwv-xhf4"
    }
  ],
  "severity": [
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "SignXML\u0027s signature verification with HMAC is vulnerable to an algorithm confusion attack"
}


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