LibreChat's IDOR in SSE Stream Subscription Allows Reading Other Users' Chats

published 2026-03-27 7 mo ago modified 2026-10-26 13 d ago also EUVD-2026-16767

cvss: 5.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 12%
public exploits: 0; none known

LibreChat is a ChatGPT clone with additional features. In versions 0.8.2-rc2 through 0.8.2-rc3, the SSE streaming endpoint `/api/agents/chat/stream/:streamId` does not verify that the requesting user owns the stream. Any authenticated user who obtains or guesses a valid stream ID can subscribe and read another user's real-time chat content, including messages, AI responses, and tool invocations. Version 0.8.2 patches the issue.

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 7 mo ago (2026-03-27)

Exploit prediction

0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/danny-avila/LibreChat/security/advisories/GHSA-f6rf-vm44-wh5g referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.3	CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

Affected products

danny-avila LibreChat

Classification

Weakness

CWE-284 Improper Access Control
CWE-639 Authorization Bypass Through User-Controlled Key

References

github.com /danny-avila/LibreChat/security/advisories/GHSA-f6rf-vm44-wh5g
exploit, vendor-advisory

Sources

CVE List CVE-2026-31950
NVD CVE-2026-31950

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary