| Component | LangChain |
| Severity | high (CVSS 7.5) |
| CVSS vector | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
| Published (NVD) | 2025-10-06 |
| Last modified | 2026-06-17 |
| Affected versions | not published yet, see the advisory |
| Fixed in | see the vendor advisory |
| Weakness | CWE-611 |
| CISA KEV | not listed |
NVD description
The HTMLSectionSplitter class in langchain-text-splitters version 0.3.8 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.
What to do
- NVD lists no fixed version yet: follow the vendor advisory below and keep LangChain off the public internet until a fix ships.
- Do not expose the component's API or UI to the internet without authentication in front of it.
Sources
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