CVE-2026-31951

{
  "id": "CVE-2026-31951",
  "sourceIdentifier": "[email protected]",
  "published": "2026-03-27T20:16:30.397",
  "lastModified": "2026-10-26T21:10:00.170",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    },
    {
      "lang": "es",
      "value": "LibreChat es un clon de ChatGPT con características adicionales. En las versiones 0.8.2-rc1 a 0.8.3-rc1, los servidores MCP (Model Context Protocol) creados por el usuario pueden incluir encabezados HTTP arbitrarios que sufren sustitución de marcadores de posición de credenciales. Un atacante puede crear un servidor MCP malicioso con encabezados que contienen ’{{LIBRECHAT_OPENID_ACCESS_TOKEN}}’ (y otros), lo que provoca que las víctimas que llaman a herramientas en ese servidor vean sus tokens OAuth exfiltrados. La versión 0.8.3-rc2 corrige el problema."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "danny-avila",
          "product": "LibreChat",
          "versions": [
            {
              "version": ">= v0.8.2-rc1, <= v0.8.3-rc1",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N",
          "baseScore": 6.8,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "REQUIRED",
          "scope": "CHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 2.3,
        "impactScore": 4.0
      },
      {
        "source": "[email protected]",
        "type": "Primary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N",
          "baseScore": 5.7,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "REQUIRED",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 2.1,
        "impactScore": 3.6
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-03-31T13:45:16.896153Z",
          "id": "CVE-2026-31951",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-200"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:librechat:librechat:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "0.8.2",
              "versionEndExcluding": "0.8.3",
              "matchCriteriaId": "0B0F03AD-B51B-4501-B292-3133DBD964A8"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:librechat:librechat:0.8.3:rc1:*:*:*:*:*:*",
              "matchCriteriaId": "482D0FE3-2AB3-47B6-982E-564A5B824464"
            }
          ]
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://github.com/danny-avila/LibreChat/security/advisories/GHSA-pmw7-gqwj-f954",
      "source": "[email protected]",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ]
    }
  ]
}