CVE-2026-85740: lightrag-hku SSRF Vulnerability via IPv6-Transition Address Bypass
Summary
CVE-2026-85740: LightRAG's native markdown parser downloads external images referenced by an uploaded markdown or textpack document. Affects lightrag-hku versions < 1.5.5. Fixed in 1.5.5. How to fix ↓
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Background
LightRAG is an open-source package designed for processing markdown documents, allowing users to upload and render textpack documents with embedded images. It features a native markdown parser that downloads external images referenced in the documents. However, a critical security flaw exists in its image-download guard, which fails to adequately validate certain IPv6 transition addresses, potentially exposing internal resources.
Vulnerability Detail
The vulnerability arises from the _validated_addresses() function in the lightrag/parser/markdown/parser.py file, which is responsible for validating image host addresses. The function incorrectly classifies certain IPv6 transition addresses (such as NAT64, IPv4-compatible, and 6to4 addresses) as globally routable. This oversight allows an attacker to exploit the server-side request forgery (SSRF) vulnerability by uploading a markdown document that references an internal address, leading to unauthorized access to sensitive internal resources, including cloud metadata and internal services.
How To Fix
Latest published version: 1.5.7 as of 23 Oct 2026
pip install --upgrade "lightrag-hku==1.5.7"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
1.5.5
This is the first release that contains the fix.
pip install --upgrade "lightrag-hku==1.5.5"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, you can disable the image download feature by setting the environment variable NATIVE_MD_IMAGE_DOWNLOAD_ENABLED to False. This will prevent the markdown parser from attempting to download external images until the package is updated.
Conclusion
The SSRF vulnerability in the lightrag-hku package poses a significant risk to applications that utilize its markdown parsing capabilities. By failing to properly validate certain IPv6 transition addresses, the package allows potential attackers to access internal resources. It is crucial for users to update to the patched version 1.5.5 to mitigate this risk and ensure the security of their applications.
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FAQ
The CVSS score of this vulnerability is 7.1, indicating a high severity level.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
Exploitation of this vulnerability can lead to unauthorized access to internal services, exposure of sensitive data, and potential compromise of cloud instance metadata.
Yes, you can temporarily disable the image download feature by setting the environment variable NATIVE_MD_IMAGE_DOWNLOAD_ENABLED to False.
The affected versions of the lightrag-hku package are 1.5.4 and earlier. The vulnerability is fixed in version 1.5.5.
References
Related vulnerabilities
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