GHSA-VFMQ-68HX-4JFW

Vulnerability from github – Published: 2026-04-21 20:38 – Updated: 2026-06-06 00:59
VLAI
Summary
lxml: Default configuration of iterparse() and ETCompatXMLParser() allows XXE to local files
Details

Impact

Using either of the two parsers in the default configuration (with resolve_entities=True) allows untrusted XML input to read local files.

Patches

lxml 6.1.0 changes the default to resolve_entities='internal', thus disallowing local file access by default.

Workarounds

Setting the resolve_entities option explicitly to resolve_entities='internal' or resolve_entities=False disables the local file access.

Resources

Original report: https://bugs.launchpad.net/lxml/+bug/2146291

The default option was changed to resolve_entities='internal' for the normal XML and HTML parsers in lxml 5.0. The default was not changed for iterparse() and ETCompatXMLParser() at the time. lxml 6.1 makes the safe option the default for all parsers.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "lxml"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-41066"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-611"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-21T20:38:44Z",
    "nvd_published_at": "2026-04-24T17:16:20Z",
    "severity": "HIGH"
  },
  "details": "### Impact\nUsing either of the two parsers in the default configuration (with `resolve_entities=True`) allows untrusted XML input to read local files.\n\n### Patches\nlxml 6.1.0 changes the default to `resolve_entities=\u0027internal\u0027`, thus disallowing local file access by default.\n\n### Workarounds\nSetting the `resolve_entities` option explicitly to `resolve_entities=\u0027internal\u0027` or `resolve_entities=False` disables the local file access.\n\n### Resources\nOriginal report: https://bugs.launchpad.net/lxml/+bug/2146291\n\nThe default option was changed to `resolve_entities=\u0027internal\u0027` for the normal XML and HTML parsers in lxml 5.0. The default was not changed for `iterparse()` and `ETCompatXMLParser()` at the time. lxml 6.1 makes the safe option the default for all parsers.",
  "id": "GHSA-vfmq-68hx-4jfw",
  "modified": "2026-06-06T00:59:15Z",
  "published": "2026-04-21T20:38:44Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lxml/lxml/security/advisories/GHSA-vfmq-68hx-4jfw"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41066"
    },
    {
      "type": "WEB",
      "url": "https://bugs.launchpad.net/lxml/+bug/2146291"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lxml/lxml"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lxml/lxml/releases/tag/lxml-6.1.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/lxml/PYSEC-2026-87.yaml"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "lxml: Default configuration of iterparse() and ETCompatXMLParser() allows XXE to local files"
}


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