CVE-2026-42203: LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format

Routine

HIGH 8.8UPGRADE

CVE-2026-42203 is a high-severity flaw (CVSS 8.8) affecting litellm. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 ho

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 69%)
CISA exploited list	No
Weakness	CWE-1336, CWE-94
Published	2026-05-08
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: litellm

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-08 04:16 UTCPublished CVE record published
2026-10-26 20:10 UTCUpdated Record last modified

litellm litellm UPGRADE

Affected: >= 1.80.5 and < 1.83.7

Fixed in: 1.83.7

Safe to downgrade to: a release before 1.80.5

1. Check installed version

apt-cache policy litellm || rpm -q litellm || litellm --version

2. UPGRADE to 1.83.7 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade litellm

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade litellm

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.80.5 (Debian / Ubuntu)

apt-cache madison litellm sudo apt install litellm=<VERSION_BEFORE_1.80.5> sudo apt-mark hold litellm

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list litellm sudo dnf downgrade litellm-<VERSION_BEFORE_1.80.5> sudo dnf versionlock add litellm

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-42203?

litellm: upgrade to 1.83.7. Exact commands for each OS are on this page.

Is CVE-2026-42203 being exploited?

CVE-2026-42203 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-42203 affect?

CVE-2026-42203 affects litellm. Severity is high (CVSS 8.8). 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

How urgent is CVE-2026-42203?

Priority 39/100. High severity

Software pages

OpenAI and LLM tools vulnerabilities

Related CVEs

CVE-2026-40217 HIGH 8.8 UPGRADE LiteLLM through 2026-04-08 allows remote attackers to execute arbitrary code via bytecode rewriting at the /gu
CVE-2026-42208 CRITICAL 9.8 EXPLOITED UPGRADE BerriAI LiteLLM SQL Injection Vulnerability
CVE-2026-42271 HIGH 8.8 EXPLOITED UPGRADE UPGRADE BerriAI LiteLLM Command Injection Vulnerability
CVE-2026-49468 CRITICAL 9.8 UPGRADE LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format
CVE-2026-12773 HIGH 7.3 UPGRADE A weakness has been identified in BerriAI litellm up to 1.59.8

References

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