Reference page — cumulative record through Saturday, October 3, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-77246

CVE-2026-77246HIGH

sooperset mcp-atlassian — MCP Atlassian: MCP HTTP Client Server-Local File Exfiltration via Unvalidated Attachment Upload Path

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  C  H  N  N    8.6   .0043   34.8     —

AFFECTED
  Product        Versions    Fixed
  mcp-atlassian  < 0.22.0 –  —

TIMELINE
  Aug 20  Reserved by GitHub_M
  Sep 22  Published (CNA: GitHub_M)
  Sep 28  EXPLOIT PUBLISHED — CVE-2026-77246 (sooperset mcp-atlassian). Public exploit reference added.
  Sep 28  RESCORED — CVE-2026-77246 (sooperset mcp-atlassian). CVSS 7.4 → 8.6 (NVD).

CWE-22, CWE-200, CWE-441 · CNA: GitHub_M · CVSS v3.1 · 4 references · NVD status: Analyzed

Description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, an HTTP transport deployment with READ_ONLY_MODE=false accepts a request without an Authorization identity and permits attacker-controlled Atlassian service headers, including X-Atlassian-Confluence-Url, to select a public attacker hostname or one allowed by MCP_ALLOWED_URL_DOMAINS. A caller can then invoke confluence_upload_attachment or the Jira attachment variant in src/mcp_atlassian/jira/attachments.py with a server-local file_path and cause the MCP process to send the file to the selected attachment endpoint. This issue is fixed in version 0.22.0.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
August 20, 2026	Reserved	Reserved by GitHub_M
September 22, 2026	Published	Published (CNA: GitHub_M)
September 28, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-77246 (sooperset mcp-atlassian). Public exploit reference added.
September 28, 2026	RESCORED	RESCORED — CVE-2026-77246 (sooperset mcp-atlassian). CVSS 7.4 → 8.6 (NVD).

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
sooperset	mcp-atlassian	—	< 0.22.0	—

Weaknesses

CWE-22 · CWE-200 · CWE-441

References (4)

https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460 [Patch]
https://github.com/sooperset/mcp-atlassian/pull/1448 [Issue Tracking, Patch]
https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0 [Release Notes]
https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-wv8v-v4c5-v75j [Exploit, Vendor Advisory]

Authoritative record: CVE-2026-77246 at cve.org

Vendors: sooperset

Weaknesses: CWE-22 · CWE-200 · CWE-441

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-77246 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Saturday, October 3, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.