CVE-2026-85740 lightrag-hku: SSRF via IPv6-transition address bypass (NAT64, IPv4-compatible, 6to4) of the native-markdown image-download guard
Attackers can bypass SSRF guards using IPv6 transition addresses to access internal resources in LightRAG deployments with NAT64/DNS64 routing.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-85740?
CVE-2026-85740 is a high-severity server-side request forgery vulnerability in HKUDS LightRAG, published on 22 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
LightRAG provides simple and fast retrieval-augmented generation. Prior to 1.5.5, _validated_addresses in lightrag/parser/markdown/parser.py evaluates the literal resolved address with ipaddress.is_global without consistently classifying an IPv4 address embedded in an IPv6 transition wrapper. A caller who can upload a Markdown or textpack document can supply an external image URL using NAT64 64:ff9b::/96 or an IPv4-compatible form that embeds a loopback, private, or cloud-metadata IPv4 address. On a deployment with compatible NAT64 or DNS64 routing, _download and _build_guarded_opener accept the wrapper and fetch the internal resource, whose body is then ingested. Current interpreter behavior already blocks some RFC 8215 and 6to4 forms, but the fixed guard handles all documented wrappers without becoming more permissive than the standard library. This issue is fixed in version 1.5.5.
Weakness: CWE-918
Which versions are affected by CVE-2026-85740?
3 open source packages ship an affected version, including lightrag-hku.
| Package | Affected | Fixed in |
|---|---|---|
lightrag-hku PyPI | All versions | 1.5.5 |
lightrag-hku PyPI | All versions | 1.5.5 |
lightrag-hku PyPI | All versions | 1.5.5 |
How do I fix CVE-2026-85740?
Upgrade lightrag-hku to 1.5.5 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-85740 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-85740 exists.
Sources
Also known as GHSA-vv3m-f8x4-7377, PYSEC-2026-4064.