CVE-2025-6985: XXE Vulnerability in langchain-ai/langchain
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.
Other sources
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.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2025-6985?
CVE-2025-6985 has a high severity rating due to its potential for exploitation via XML External Entity (XXE) attacks.
How do I fix CVE-2025-6985?
To fix CVE-2025-6985, upgrade to a version of langchain-text-splitters that does not allow unsafe XSLT parsing.
What software is affected by CVE-2025-6985?
CVE-2025-6985 affects langchain-text-splitters version 0.3.8 and up to lxml version 4.9.x.
What type of attack does CVE-2025-6985 enable?
CVE-2025-6985 enables XML External Entity (XXE) attacks due to improper handling of XSLT stylesheets.
Is CVE-2025-6985 related to any specific libraries?
Yes, CVE-2025-6985 is specifically related to the langchain-text-splitters library and the lxml library.