ghsa-pwfw-mgfj-7g3g
Vulnerability from github
Published
2019-10-08 16:30
Modified
2024-09-20 16:47
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7 (High) - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Summary
ecdsa Denial of Service vulnerability in signature verification and signature malleability
Details

possible DoS in signature verification and signature malleability

Impact

Code using VerifyingKey.verify() and VerifyingKey.verify_digest() may receive exceptions other than the documented BadSignatureError when signatures are malformed. If those other exceptions are not caught, they may lead to program termination and thus Denial of Service

Code using VerifyingKey.verify() and VerifyingKey.verify_digest() with sigdecode option using ecdsa.util.sigdecode_der will accept signatures even if they are not properly formatted DER. This makes the signatures malleable. It impacts only applications that later sign the signatures or verify signatures of signatures, e.g. Bitcoin.

All versions between 0.5 and 0.13.2 (inclusive) are thought to be vulnerable. Code before 0.5 may be vulnerable but didn't receive extended analysis to rule this issue out.

Patches

The patches have been merged to master branch in https://github.com/warner/python-ecdsa/pull/115. The backported patches for a release in the 0.13 branch are in https://github.com/warner/python-ecdsa/pull/124

They are part of the 0.13.3 release.

There are no plans to backport them to earlier releases.

Workarounds

It may be possible to prevent the Denial of Service by catching also UnexpectedDER, IndexError and AssertionError exceptions. That list hasn't been verified to be complete though. If those exceptions are raised, the signature verification process should consider the signature to be invalid.

To remediate signature malleability and the Denial of Service vulnerability, it may be possible to first verify that the signature is properly DER formatted ECDSA-Sig-Value, as defined in RFC3279, before passing it to verify() or verify_digest() methods. If the signature is determined to not follow the DER or encode a different structure, the signature verification process should consider the signature to be invalid.

References

https://en.bitcoinwiki.org/wiki/Transaction_Malleability

For more information

If you have any questions or comments about this advisory please open an issue in python-ecdsa project.

Show details on source website

To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "ecdsa"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.13.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2019-14853"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-391",
      "CWE-755"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2020-06-16T20:41:53Z",
    "nvd_published_at": "2019-11-26T13:15:00Z",
    "severity": "HIGH"
  },
  "details": "## possible DoS in signature verification and signature malleability \n\n### Impact\nCode using `VerifyingKey.verify()` and `VerifyingKey.verify_digest()` may receive exceptions other than the documented `BadSignatureError` when signatures are malformed. If those other exceptions are not caught, they may lead to program termination and thus Denial of Service\n\nCode using `VerifyingKey.verify()` and `VerifyingKey.verify_digest()` with `sigdecode` option using `ecdsa.util.sigdecode_der` will accept signatures even if they are not properly formatted DER. This makes the signatures malleable. It impacts only applications that later sign the signatures or verify signatures of signatures, e.g. Bitcoin.\n\nAll versions between 0.5 and 0.13.2 (inclusive) are thought to be vulnerable. Code before 0.5 may be vulnerable but didn\u0027t receive extended analysis to rule this issue out.\n\n### Patches\nThe patches have been merged to `master` branch in https://github.com/warner/python-ecdsa/pull/115.\nThe backported patches for a release in the 0.13 branch are in https://github.com/warner/python-ecdsa/pull/124\n\nThey are part of the 0.13.3 release.\n\nThere are no plans to backport them to earlier releases.\n\n### Workarounds\nIt may be possible to prevent the Denial of Service by catching also `UnexpectedDER`, `IndexError` and `AssertionError` exceptions. That list hasn\u0027t been verified to be complete though. If those exceptions are raised, the signature verification process should consider the signature to be invalid.\n\nTo remediate signature malleability and the Denial of Service vulnerability, it may be possible to first verify that the signature is properly DER formatted ECDSA-Sig-Value, as defined in [RFC3279](https://tools.ietf.org/html/rfc3279), before passing it to `verify()` or `verify_digest()` methods. If the signature is determined to not follow the DER or encode a different structure, the signature verification process should consider the signature to be invalid.\n\n### References\nhttps://en.bitcoinwiki.org/wiki/Transaction_Malleability\n\n### For more information\nIf you have any questions or comments about this advisory please open an issue in [python-ecdsa](https://github.com/warner/python-ecdsa/issues) project.\n",
  "id": "GHSA-pwfw-mgfj-7g3g",
  "modified": "2024-09-20T16:47:14Z",
  "published": "2019-10-08T16:30:17Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/warner/python-ecdsa/security/advisories/GHSA-pwfw-mgfj-7g3g"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-14853"
    },
    {
      "type": "WEB",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-14853"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/ecdsa/PYSEC-2019-177.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/warner/python-ecdsa"
    },
    {
      "type": "WEB",
      "url": "https://github.com/warner/python-ecdsa/releases/tag/python-ecdsa-0.13.3"
    },
    {
      "type": "WEB",
      "url": "https://seclists.org/bugtraq/2019/Dec/33"
    },
    {
      "type": "WEB",
      "url": "https://www.debian.org/security/2019/dsa-4588"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "ecdsa Denial of Service vulnerability in signature verification and signature malleability"
}


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