LangChain Text Splitters is vulnerable to XML External Entity (XXE) attacks due to unsafe XSLT parsing
The HTMLSectionSplitter class in langchain-text-splitters is vulnerable to XML External Entity (XXE) attacks due to unsafe XSLT parsing. This vulnerability arises because the class allows the use of arbitrary XSLT stylesheets, which are parsed using lxml.etree.parse() and lxml.etree.XSLT() without any hardening measures. In lxml versions up to 4.9.x, external entities are resolved by default, allowing attackers to read arbitrary local files or perform outbound HTTP(S) fetches. In lxml versions 5.0 and above, while entity expansion is disabled, the XSLT document() function can still read any URI unless XSLTAccessControl is applied. This vulnerability allows remote attackers to gain read-only access to any file the LangChain process can reach, including sensitive files such as SSH keys, environment files, source code, or cloud metadata. No authentication, special privileges, or user interaction are required, and the issue is exploitable in default deployments that enable custom XSLT.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | langchain-text-splitters | < 0.3.9 | 0.3.9 |
References
- https://nvd.nist.gov/vuln/detail/CVE-2025-6985
- https://github.com/langchain-ai/langchain/pull/31819
- https://github.com/langchain-ai/langchain/commit/43eef435505a1c907227b724c0c760ad5fc01790
- https://github.com/langchain-ai/langchain
- https://huntr.com/bounties/cf78abbb-df3b-43de-b6ee-132b73ff8331
- https://pypi.org/project/langchain-text-splitters
- https://github.com/advisories/GHSA-m42m-m8cr-8m58
- CVSS vector
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N- Weakness (CWE)
CWE-611- Platform
- Python (PyPI)
- Package
langchain-text-splitters- Disclosed
- 06.10.2025
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-1520 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-m42m-m8cr-8m58 - CC BY 4.0
Vulnerability history: langchain-text-splitters
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 10.2025 04.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 1
Disclosures per year
- 2025: 1
- 2026: 1
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LangChain Text Splitters is vulnerable to XML External Entity (XXE) attacks due to unsafe XSLT parsing this entry
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