CVE-2024-0243 in LangChain
Summary
by MITRE • 02/26/2024
With the following crawler configuration:
```python from bs4 import BeautifulSoup as Soup
url = "https://example.com" loader = RecursiveUrlLoader( url=url, max_depth=2, extractor=lambda x: Soup(x, "html.parser").text ) docs = loader.load() ```
An attacker in control of the contents of `https://example.com` could place a malicious HTML file in there with links like "https://example.completely.different/my_file.html" and the crawler would proceed to download that file as well even though `prevent_outside=True`.
https://github.com/langchain-ai/langchain/blob/bf0b3cc0b5ade1fb95a5b1b6fa260e99064c2e22/libs/community/langchain_community/document_loaders/recursive_url_loader.py#L51-L51
Resolved in https://github.com/langchain-ai/langchain/pull/15559
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 02/26/2025
The vulnerability CVE-2024-0243 represents a critical path traversal issue within the RecursiveUrlLoader implementation of the Langchain community library. This flaw allows attackers to bypass URL restriction mechanisms through carefully crafted HTML content that contains external links, effectively enabling unauthorized access to resources outside the originally specified domain. The vulnerability stems from improper validation of URL origins during recursive document loading operations, creating a security gap that can be exploited by malicious actors controlling the target website's content.
The technical implementation of this vulnerability occurs when the RecursiveUrlLoader processes HTML content and extracts links without properly verifying that these links remain within the configured domain boundaries. The extractor function specifically designed to parse HTML content fails to enforce domain restrictions, allowing the crawler to follow external links even when the prevent_outside=True parameter is set. This behavior directly violates the intended security model where recursive URL loading should remain confined to the specified base URL domain. The flaw manifests in the loader's handling of relative and absolute URLs, where external references are not properly sanitized or rejected during the crawling process.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables potential attack vectors including cross-site request forgery, data exfiltration, and unauthorized access to internal systems. An attacker controlling the content of the initial URL can craft HTML documents containing links to internal resources, cloud storage endpoints, or other sensitive systems that may be accessible from the crawling environment. This creates a pathway for privilege escalation and lateral movement within network boundaries, particularly when the crawler executes in environments with elevated permissions or access to internal resources. The vulnerability is particularly concerning in automated scraping or document ingestion scenarios where the crawler may be processing untrusted content from multiple sources.
Security mitigations for this vulnerability should focus on implementing robust URL validation mechanisms within the RecursiveUrlLoader component. The fix requires ensuring that all extracted links undergo strict domain verification before being processed, with proper enforcement of the prevent_outside parameter regardless of URL format. Organizations should also consider implementing additional network segmentation and access controls around systems running recursive URL crawlers to limit potential damage from such vulnerabilities. This vulnerability aligns with CWE-22 Path Traversal and CWE-200 Information Exposure, and maps to ATT&CK techniques including T1083 File and Directory Discovery and T1566 Phishing, as it enables unauthorized access to resources through crafted content manipulation.