LibreChat's MCP Server Header Injection Enables OAuth Token Theft

MITRE NVD CVE.ORG Print: PDF PDF

Summary

CVECVE-2026-31951
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-03-27 20:16:30 UTC
Updated2026-03-30 20:29:45 UTC
DescriptionLibreChat 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.

Risk And Classification

Primary CVSS: v3.1 5.7 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N

EPSS: 0.000320000 probability, percentile 0.092710000 (date 2026-04-01)

Problem Types: CWE-200 | CWE-200 CWE-200: Exposure of Sensitive Information to an Unauthorized Actor

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary5.7MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N
3.1[email protected]Secondary6.8MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N
3.1CNADECLARED6.8MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Librechat Librechat All All All All
Application Librechat Librechat 0.8.3 rc1 All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Danny-avila LibreChat affected >= v0.8.2-rc1, <= v0.8.3-rc1 Not specified

References

ReferenceSourceLinkTags
github.com/danny-avila/LibreChat/security/advisories/GHSA-pmw7-gqwj-f954 [email protected] github.com Exploit, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
© CVE.report 2026 |

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

CVE.report and Source URL Uptime Status status.cve.report