How severe is CVE-2026-6607?

No CVSS score has been assigned to CVE-2026-6607 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-6607?

CVE-2026-6607 affects the following packages: fschat (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-6607?

The records we use list no patched version of fschat for CVE-2026-6607. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

How do I detect CVE-2026-6607 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fschat, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-6607 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-6607 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-6607 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-6607?

CVE-2026-6607 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 50th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-6607?

CVE-2026-6607 is classified as Uncontrolled Resource Consumption (CWE-400), CWE-404 (CWE-404). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-6607 published, and has it been updated?

CVE-2026-6607 was published on April 20, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2026-6607: fschat

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-6607.

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs50th percentile — riskier than 50% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍fschat

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

A security vulnerability has been detected in lm-sys fastchat up to 0.2.36. This issue affects the function api_generate of the component Worker API Endpoint. The manipulation leads to resource consumption. The attack can be initiated remotely. The exploit has been disclosed publicly and may be used. The identifier of the patch is c9e84b89c91d45191dc24466888de526fa04cf33. It is suggested to install a patch to address this issue. Commit ff66426 patched this issue in api_generate of base_model_worker.py and did miss other entry points.

Affected Packages

1 total

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`fschat`	all versions	No fix

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fschat, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
The records we use list no patched version of fschat for CVE-2026-6607. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
Mitigate without a patch
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

A security vulnerability has been detected in lm-sys fastchat up to 0.2.36. This issue affects the function api_generate of the component Worker API Endpoint. The manipulation leads to resource consumption. The attack can be initiated remotely. The exploit has been disclosed publicly and may be used. The identifier of the patch is c9e84b89c91d45191dc24466888de526fa04cf33. It is suggested to install a patch to address this issue. Commit ff66426 patched this issue in api_generate of base_model_worker.py and did miss other entry points.

O3 Security · Impact-Aware SCA

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CVE-2026-6607 — fschat