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Vulnerability · Published Jan 22, 2026 · Assigned by GitHub_M

CVE-2026-24055Langfuse Slack OAuth Installation Endpoint Lacks Authentication, Enabling Arbitrary Project Linking

Medium 6.3

In plain English

A medium-severity improper access control in langfuse from langfuse. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 38% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.

Severity (CVSS 4.0)6.3Medium
Exploit odds (30 days)0.4%top 62.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack tooling1Public PoC

Official description

Langfuse is an open source large language model engineering platform. In versions 3.146.0 and below, the /api/public/slack/install endpoint initiates Slack OAuth using a projectId provided by the client without authentication or authorization. The projectId is preserved throughout the OAuth flow, and the callback stores installations based on this untrusted metadata. This allows an attacker to bind their Slack workspace to any project and potentially receive changes to prompts stored in Langfuse Prompt Management. An attacker can replace existing Prompt Slack Automation integrations or pre-register a malicious one, though the latter requires an authenticated user to unknowingly configure it despite visible workspace and channel indicators in the UI. This issue has been fixed in version 3.147.0.

Affected products (as reported)

VendorProductVersions
langfuse langfuse >= 3.89.0, < 3.147.0

Weakness: CWE-284 · Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

References