Medium Denial of service exploit reference

CVE-2026-6607 — lm-sys fastchat Worker API Endpoint api_generate resource consumption

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.

Published Apr 20, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: VulDB

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.7% (30-day exploitation probability)+8
Technical severity (medium)+3
CISA SSVC: exploitation "poc"+5
Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.74%

ahead of 54% of scored CVEs · Oct 14, 2026

Affects

Lmsys

Fastchat

CVSS base

5.3

Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Proof of concept

none · proof-of-concept · active

Automatable

Yes

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Lmsys Fastchat).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (denial of service), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Lmsys	Fastchat	version 0.2.28version 0.2.19version 0.2.20version 0.2.21version 0.2.22version 0.2.23version 0.2.24version 0.2.25 and 29 more version 0.2.26version 0.2.27version 0.2.18version 0.2.29version 0.2.30version 0.2.31version 0.2.32version 0.2.33version 0.2.34version 0.2.35version 0.2.36version 0.2.9version 0.2.1version 0.2.2version 0.2.3version 0.2.4version 0.2.5version 0.2.6version 0.2.7version 0.2.8version 0.2.0version 0.2.10version 0.2.11version 0.2.12version 0.2.13version 0.2.14version 0.2.15version 0.2.16version 0.2.17	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
6.9	CVSS 4.0	Medium	—	—	VulDB via CVE Program (cve.org) e CISA ADP
5.5	CVSS 4.0	Medium	—	—	cna@vuldb.com via NIST National Vulnerability Database
5.3	CVSS 3.1	Medium	3.9	1.4	cna@vuldb.com via NIST National Vulnerability Database
5.3	CVSS 3.1	Medium	—	—	VulDB via CVE Program (cve.org) e CISA ADP
5.3	CVSS 3.0	Medium	—	—	VulDB via CVE Program (cve.org) e CISA ADP
5.0	CVSS 2.0	Medium	10.0	2.9	cna@vuldb.com via NIST National Vulnerability Database
5.0	CVSS 2.0	Medium	—	—	VulDB via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L (score shown at the top: cna@vuldb.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-400 · Uncontrolled Resource Consumption

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.74%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Track CPU/memory spikes and availability drops correlated with request patterns.

web/proxy/WAF logsnetwork IDS/IPSresource metrics

Timeline

What happened to this CVE, newest first.

2026
Affected products added · lm-sys/fastchat
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 5.3
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Deferred
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Apr 20, 2026 · VulDB

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

8 on the record

github.com/lm-sys/FastChat/commit/c9e84b89c91d45191dc24466888de526fa04cf33
patch, NIST National Vulnerability Database
github.com/lm-sys/FastChat/pull/3835
issue-tracking, patch, NIST National Vulnerability Database
vuldb.com/submit/792227
third-party-advisory, NIST National Vulnerability Database
github.com/lm-sys/FastChat/
product, NIST National Vulnerability Database
vuldb.com/vuln/358242
vdb-entry, technical-description, NIST National Vulnerability Database
vuldb.com/vuln/358242/cti
signature, permissions-required, NIST National Vulnerability Database
gist.github.com/YLChen-007/87216a2d97a882d619e11dc67cd473b5
exploit, NIST National Vulnerability Database
github.com/lm-sys/FastChat/issues/3833
issue-tracking, NIST National Vulnerability Database

Elsewhere on this site

Lmsys
every CVE for this vendor

Denial of service
same class

CWE-400
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-6608 lm-sys fastchat Arena Side-by-Side View add_text control flow Apr 20, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-6607 is "lm-sys fastchat Worker API Endpoint api_generate resource consumption", rated Medium. It affects Fastchat (Lmsys); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.3 describes technical severity. EPSS 0.74% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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