LiteLLM: LiteLLM Proxy has server-side request forgery via the `user_config` request parameter
LiteLLM
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- Severity
- Medium, CVSS 5.3
- CVSS vector
- CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N
- Record
- CVE-2026-59823
- Affects
- LiteLLM
- Known exploited
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Published
- Record first published by the source
- September 17, 2026
- Source last modified
- September 17, 2026
Description
Summary
A server-side request forgery in LiteLLM Proxy lets an authenticated caller redirect the
proxy's outbound request to a host of their choosing by smuggling an api_base inside the
user_config request body, bypassing the existing parameter guard.
Details
LiteLLM Proxy validates request bodies with is_request_body_safe, which blocks the
api_base and base_url parameters but does not cover user_config. The user_config
object is used to build the outbound router for a request, so a caller can place an
api_base inside it and reach an arbitrary host. The guard only inspected the two
top-level keys, so the same api_base nested inside user_config was never checked.
Exploitation requires a valid virtual key.
Impact
An authenticated caller can make the proxy issue server-side requests to internal or external hosts of their choosing, reaching endpoints the caller cannot otherwise access.
Affected / Patched
Affected: <= 1.83.8
Patched: 1.83.9
Remediation
Upgrade to 1.83.9 or later (released 2026-04-17).
Description quoted from the NVD record.