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LiteLLM Proxy CVE-2026-42203

| EUVD-2026-28502 HIGH
Improper Neutralization of Special Elements Used in a Template Engine (CWE-1336)
2026-05-08 GitHub_M GHSA-xqmj-j6mv-4862
8.6
CVSS 4.0
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CVSS VectorNVD

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
X

Lifecycle Timeline

5
Patch available
May 08, 2026 - 05:01 EUVD
Source Code Evidence Fetched
May 08, 2026 - 04:32 vuln.today
Analysis Generated
May 08, 2026 - 04:32 vuln.today
CVSS changed
May 08, 2026 - 04:22 NVD
8.6 (HIGH)
CVE Published
May 08, 2026 - 03:36 nvd
HIGH 8.6

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 2 pypi packages depend on litellm (1 direct, 1 indirect)

Ecosystem-wide dependent count for version 1.80.5.

DescriptionNVD

LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format. From version 1.80.5 to before version 1.83.7, the POST /prompts/test endpoint accepted user-supplied prompt templates and rendered them without sandboxing. A crafted template could run arbitrary code inside the LiteLLM Proxy process. The endpoint only checks that the caller presents a valid proxy API key, so any authenticated user could reach it. Depending on how the proxy is deployed, this could expose secrets in the process environment (such as provider API keys or database credentials) and allow commands to be run on the host. This issue has been patched in version 1.83.7.

AnalysisAI

Server-side template injection in LiteLLM Proxy versions 1.80.5 through 1.83.6 allows authenticated users to execute arbitrary code via the POST /prompts/test endpoint. Any user with a valid proxy API key can submit malicious prompt templates that escape sandboxing and run commands in the proxy server process, exposing environment secrets like provider API keys and database credentials. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Obtain valid proxy API key
Delivery
Send crafted SSTI payload to POST /prompts/test
Exploit
Template engine executes arbitrary Python code
Execution
Access process environment variables
Persist
Exfiltrate provider API keys and credentials
Impact
Execute system commands on proxy host

Vulnerability AssessmentAI

Exploitation Valid LiteLLM proxy API key for authentication (CVSS PR:L). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment Real-world risk is high but not critical due to authentication requirement limiting attack surface. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An authenticated attacker with a valid LiteLLM proxy API key crafts a malicious prompt template containing server-side template injection payloads (e.g., Jinja2 syntax accessing Python object internals like {{''.__class__.__mro__[1].__subclasses__()}}). They submit this payload to POST /prompts/test, which the proxy renders without sandboxing. …
Remediation Upgrade to LiteLLM version 1.83.7-stable or later, which implements sandboxed template rendering that blocks dangerous object attribute access (confirmed fix at https://github.com/BerriAI/litellm/releases/tag/v1.83.7-stable). … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours: Identify all LiteLLM Proxy instances and document their version numbers; audit and rotate all API keys with proxy access privileges. …

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Vendor StatusVendor

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CVE-2026-42203 vulnerability details – vuln.today

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