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CVE-2026-54030 danny-avila CVE debrief

CVE-2026-54030 is a high-severity vulnerability in LibreChat, an enhanced ChatGPT clone. The issue lies in the MCP OAuth implementation, which fails to validate the resource parameter from OAuth Protected Resource metadata. This oversight enables a malicious MCP server to steal access tokens intended for a legitimate server. The vulnerability was publicly disclosed on June 25, 2026, and was fixed in LibreChat version 0.8.5 on June 29, 2026. The CVSS score for this vulnerability is 8, indicating a high level of severity. Users of LibreChat should ensure they are running version 0.8.5 or later to mitigate this vulnerability.

Vendor
danny-avila
Product
LibreChat
CVSS
HIGH 8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-25
Original CVE updated
2026-06-29
Advisory published
2026-06-25
Advisory updated
2026-06-29

Who should care

Developers and administrators using LibreChat, especially those who have integrated MCP OAuth functionality, should be aware of this vulnerability. They should verify their current version and update to 0.8.5 or later if necessary. Additionally, users of LibreChat should be cautious when interacting with MCP servers, as a malicious server could potentially steal access tokens.

Technical summary

The vulnerability in LibreChat's MCP OAuth implementation allows a malicious MCP server to steal access tokens. This is possible because the resource parameter from OAuth Protected Resource metadata is not validated. The issue was introduced in an earlier version of LibreChat and was fixed in version 0.8.5. The CVSS vector for this vulnerability is CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N, indicating a high level of severity. The weakness associated with this vulnerability is CWE-346.

Defensive priority

High priority should be given to updating LibreChat to version 0.8.5 or later. In the meantime, defenders should monitor for suspicious activity related to MCP OAuth interactions and consider implementing additional security measures to protect access tokens.

Recommended defensive actions

  • Update LibreChat to version 0.8.5 or later
  • Monitor for suspicious activity related to MCP OAuth interactions
  • Implement additional security measures to protect access tokens
  • Review and update MCP server configurations to prevent malicious activity
  • Consider implementing compensating controls to mitigate the vulnerability

Evidence notes

The CVE record and NVD detail provide information on the vulnerability and its impact. The source item URL provides additional context on the vulnerability and its mitigation. The mitigation or vendor reference provides guidance on updating to version 0.8.5 or later.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-54030 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-54030

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-54030 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-54030

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.