CVE-2026-45018: Chainlit is a Python framework for building production-ready conversational AI applications

This week

CRITICAL 9.8REMOTE

CVE-2026-45018 is a critical-severity flaw (CVSS 9.8) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Chainlit is a Python framework for building production-ready conversational AI applications. From 2.4.0rc0 until 2.12.0, Chainlit deployments with features.mcp.enabled set to true in .chainlit/config.toml expose the POST /mcp endpoint without requiring authentication. For stdio transport, the endpoint accepts a user-controlled fullCommand string. The validate_mcp_command() function in backend/chainlit/mcp.py checks only the executable name agains

Why this priority

Critical severity
CISA SSVC: public proof of concept
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.1% (top 35%)
CISA exploited list	No
Weakness	CWE-78
Published	2026-08-25
Last modified	2026-09-09

Publisher (CNA): GitHub, Inc.

Last updated 2026-09-09 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-08-25 20:16 UTCPublished CVE record published
2026-09-09 21:07 UTCUpdated Record last modified

Exact fixes by distribution

Python (pip) · chainlit · FIXED · 2.12.0 · vulnerable: >= 2.4.0rc0, <= 2.11.1 · source

pip install --upgrade "chainlit>=2.12.0" pip show chainlit

Fedora 46 · gcl · FIXED · 2.7.1-12.fc46 · FEDORA-2026-ff383a759b · source

sudo dnf upgrade --advisory=FEDORA-2026-ff383a759b

Fedora ELN · mozjs140 · FIXED · 140.13.0-5.eln159 · FEDORA-2026-f7ed0026e0 · source

sudo dnf upgrade --advisory=FEDORA-2026-f7ed0026e0

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/Chainlit/chainlit/commit/0565fd0eccb915fce159929598b053ed79f6e0c9
Write-up: github.com/Chainlit/chainlit/releases/tag/2.12.0

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-2026-45018?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-45018 being exploited?

CVE-2026-45018 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-2026-45018 affect?

CVE-2026-45018 affects affected software. Severity is critical (CVSS 9.8). Chainlit is a Python framework for building production-ready conversational AI applications. From 2.4.0rc0 until 2.12.0, Chainlit deployments with features.mcp.enabled set to true in .chainlit/config.toml expose the POST /mcp endpoint witho

How urgent is CVE-2026-45018?

Priority 62/100. Critical severity; CISA SSVC: public proof of concept; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

Python vulnerabilities

References

← Back to latest CVEs