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High, CVSS 8.8amended

MCP Atlassian: SSRF Protection Bypass

CVE-2026-77274GHSA-hgcf-4mq8-5266

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (mcp-atlassian 0.22.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.8 · 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 · score source
EPSS
  • CVE-2026-77274: 0.33% estimated exploitation activity in the next 30 days; percentile 26.24 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Environment - Project: sooperset/mcp-atlassian - Affected function: validateurlforssrf() - Affected path: header-based Jira/Confluence URL authentication flow - Tested endpoint: POST /mcp - Tested version: 2.14.5 Description The SSRF protection in validateurlforssrf() can be bypassed with a URL containing a backslash before userinfo-like syntax. Affected code: Payload: For this input, urllib.parse.urlparse() treats the hostname as: Therefore, validateurlforssrf() validates www.baidu.com instead of 127.0.0.1. However, the downstream request made through the Atlassian client / requests.Session reaches the local service: This allows an attacker-controlled Jira URL to target loopback or internal services. Proof of Concept Start a local HTTP server: Start mcp-atlassian with streamable HTTP transport on port 9000. Initialize an MCP session with the malicious Jira URL: Send the initialized notification using the returned Mcp-Session-Id: Trigger Jira fetcher creation and token validation:…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-hgcf-4mq8-5266

  2. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 2 · amended ·

    Amended from osv record GHSA-hgcf-4mq8-5266

  4. Revision 1 · created ·

    Published from ghsa record GHSA-hgcf-4mq8-5266

Agent brief

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# Patch Next advisory brief: CVE-2026-77274

Advisory: MCP Atlassian: SSRF Protection Bypass
IDs: CVE-2026-77274, GHSA-hgcf-4mq8-5266
Record: https://patchnext.com/advisories/cve-2026-77274 (revision 4, source checked 26 Oct 2026, 13:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mcp-atlassian 0.22.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI mcp-atlassian: affected < 0.22.0; fixed in 0.22.0

## Suggested inspection (read-only)
- `python -m pip show mcp-atlassian`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on mcp-atlassian.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-hgcf-4mq8-5266 (GitHub-reviewed advisory GHSA-hgcf-4mq8-5266 lists affected ranges: PyPI mcp-atlassian >=0 <0.22.0)
- Verified: https://osv.dev/vulnerability/GHSA-hgcf-4mq8-5266 (OSV record GHSA-hgcf-4mq8-5266 lists affected ranges: PyPI mcp-atlassian >=0 <0.22.0 (fixed))

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