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Advisory record · GHSA-hgcf-4mq8-5266

MCP Atlassian: SSRF Protection Bypass

CVSS 8.8 HighEPSS 0.0033 · 26th percentile

Published by the GitHub Advisory Database at 22 Sept 2026, 20:36 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-hgcf-4mq8-5266 · CVE-2026-77274 · PYSEC-2026-4096
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.

The SSRF validation in mcp-atlassian versions before 0.22.0 can be bypassed with a crafted URL containing a backslash before userinfo-like syntax, so the URL check validates one host while requests go to another. An attacker who can supply the X-Atlassian-Jira-Url or X-Atlassian-Confluence-Url header can make the server send requests to loopback or internal services. Upgrade to mcp-atlassian 0.22.0 or later. The source gives few details on the exact trigger conditions.

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
8.8 High 4.0 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0033, the 26th 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.