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TI-2026-24495 Aliases CVE-2026-31951

LibreChat's MCP Server Header Injection Enables OAuth Token Theft

Priority MEDIUM 63CWE-200Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
Required
Attack complexity
Low
Impact type
Information disclosure
Confidentiality · integrity · availability
High · None · None
Fix status
No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-200.

Summary

LibreChat is a ChatGPT clone with additional features. In versions 0.8.2-rc1 through 0.8.3-rc1, user-created MCP (Model Context Protocol) servers can include arbitrary HTTP headers that undergo credential placeholder substitution. An attacker can create a malicious MCP server with headers containing `{{LIBRECHAT_OPENID_ACCESS_TOKEN}}` (and others), causing victims who call tools on that server to have their OAuth tokens exfiltrated. Version 0.8.3-rc2 fixes the issue.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00253 16th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
danny-avilaLibreChatv0.8.2-rc1 – v0.8.3-rc1—No fix listedCNA
  • LibreChat Vendordanny-avila Affected v0.8.2-rc1 – v0.8.3-rc1 Fixed in — No fix listed CNA

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:a:librechat:librechat:*:*:*:*:*:*:*:*0.8.2 to before 0.8.3Vulnerabledanny-avila
cpe:2.3:a:librechat:librechat:0.8.3:rc1:*:*:*:*:*:*0.8.3 rc1Vulnerabledanny-avila
  • cpe:2.3:a:librechat:librechat:*:*:*:*:*:*:*:* Versions 0.8.2 to before 0.8.3 Vulnerable ·danny-avila
  • cpe:2.3:a:librechat:librechat:0.8.3:rc1:*:*:*:*:*:* Versions 0.8.3 rc1 Vulnerable ·danny-avila

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-31951

References

Exploit 1

  • TI-2026-25134 LibreChat Exfiltrates Server Secrets via MCP Server URL Injection CVSS 3.1CRITICAL 9.6
  • TI-2026-17862 LibreChat MCP Stdio Remote Command Execution CVSS 3.1CRITICAL 9.9
  • TI-2026-38976 LibreChat: Missing Resource Parameter Validation in MCP OAuth Flow CVSS 3.1CRITICAL 9.3
  • TI-2024-27763 LibreChat through 0.7.4-rc1 has incorrect access control for message updates. CVSS 3.1CRITICAL 9.8
  • TI-2024-10347 Path Traversal in danny-avila/librechat CVSS 3.0HIGH 8.8
  • TI-2026-25682 In LibreChat 0.8.1-rc2, a logged-in user obtains a JWT for both the LibreChat API and the RAG API. CVSS 3.1CRITICAL 9.0
See all 50 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences