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Advisory record · GHSA-49xv-9743-pw8w

MCP Atlassian: SSRF via DNS Rebinding in Header-Based Authentication Flow

CVSS 5.9 MediumEPSS 0.0029 · 21st percentile

Published by the GitHub Advisory Database at 22 Sept 2026, 20:35 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
mcp-atlassianPyPI<0.22.00.22.0
Identifiers
GHSA-49xv-9743-pw8w · CVE-2026-77265 · PYSEC-2026-4083
Weakness (CWE)
CWE-918
Tags
Published
22 Sept 2026
Updated
1 Oct 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Versions of mcp-atlassian before 0.22.0 are vulnerable to server-side request forgery through DNS rebinding in the header-based authentication flow. The SSRF check resolves the hostname once, but the actual request resolves it again later, so a remote, unauthenticated attacker could point the request at internal addresses such as cloud metadata services. The source describes the attack as probabilistic and limited to deployments that accept header-based personal access tokens. Upgrade to mcp-atlassian 0.22.0 or later. No workaround is listed.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
5.9 Medium 3.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0029, the 21st percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:09 UTC First seen by agentprime
  2. 31 Oct 2026, 14:09 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.