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CVE-2026-77261

Status: AnalyzedHigh (8.5)—

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, _make_ssrf_safe_hook is omitted from JiraFetcher and ConfluenceFetcher sessions created through the basic-auth and oauth_pat branches. If an attacker-controlled or compromised configured Atlassian instance returns a redirect to an internal address, those sessions can follow the redirect without revalidating its destination. This issue is fixed in version 0.22.0.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

MCP Atlassian permite SSRF (CWE-918) sin validación de redirecciones en sesiones autenticadas (PR:L). Acceso a recursos internos a través de proxy sin revalidación (T1090.001) y potencial exfiltración de credenciales almacenadas (T1552.007).

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Privileged Account ManagementNetwork SegmentationVulnerability ScanningUser Account ManagementThreat Intelligence ProgramNetwork Intrusion Prevention

Affected technologies (1)

Mcp-atlassian — MCP Atlassian

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2026-77261",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-77261",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-09-22T19:07:42.566871Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
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        "source": "security-advisories@github.com",
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          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "NONE",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 4.7,
        "exploitabilityScore": 1.8
      },
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "CHANGED",
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          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
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      }
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    {
      "source": "security-advisories@github.com",
      "affectedData": [
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          "vendor": "sooperset",
          "product": "mcp-atlassian",
          "versions": [
            {
              "status": "affected",
              "version": "< 0.22.0"
            }
          ]
        }
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  ],
  "published": "2026-09-22T18:17:18.497",
  "references": [
    {
      "url": "https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460",
      "tags": [
        "Patch"
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    {
      "url": "https://github.com/sooperset/mcp-atlassian/pull/1448",
      "tags": [
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      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0",
      "tags": [
        "Release Notes"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-6529-c226-h328",
      "tags": [
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        "Vendor Advisory"
      ],
      "source": "security-advisories@github.com"
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  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "description": [
        {
          "lang": "en",
          "value": "CWE-918"
        }
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  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, _make_ssrf_safe_hook is omitted from JiraFetcher and ConfluenceFetcher sessions created through the basic-auth and oauth_pat branches. If an attacker-controlled or compromised configured Atlassian instance returns a redirect to an internal address, those sessions can follow the redirect without revalidating its destination. This issue is fixed in version 0.22.0."
    }
  ],
  "lastModified": "2026-09-25T17:36:32.787",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:mcp-atlassian:mcp_atlassian:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "5B21EB9C-719D-42B9-8F6D-BE4EDC5D39AD",
              "versionEndExcluding": "0.22.0"
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  "sourceIdentifier": "security-advisories@github.com"
}