[mcp-atlassian] Authentication bypass in HTTP transport: AtlassianOpaqueTokenVerifier accepts any non-empty token

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

10.0 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

EPSS

• CVE-2026-77244: 0.35% estimated exploitation activity in the next 30 days; percentile 28.25 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Description mcp-atlassian deploys in two common patterns: Pattern A (single-user, server-side credentials): operator sets JIRAUSERNAME + JIRAAPITOKEN (or CONFLUENCEUSERNAME + CONFLUENCEAPITOKEN) in environment variables. Server uses these to call Jira/Confluence. This is the documented quickstart pattern. Pattern B (multi-user, OAuth or per-request PAT): operator sets up OAuth proxy or accepts per-user tokens via Authorization or service headers. The authentication mechanism in HTTP transport has two issues that combine to permit unauthenticated access to Pattern A deployments: 1. AtlassianOpaqueTokenVerifier.verifytoken() at src/mcpatlassian/utils/tokenverifier.py accepts any non-empty string as a valid token: async def verifytoken(self, token: str) - AccessToken | None: if not token: return None scopes = self.requiredscopes or [] return AccessToken( token=token, clientid="atlassian", scopes=scopes, expiresat=int(time.time()) + 86400 30, ) The docstring documents this: "we accept…

Published by the source

22 Sep 2026, 20:36 UTC

Last modified by the source

1 Oct 2026, 17:55 UTC

Source last checked

26 Oct 2026, 13:54 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-wrhw-j3f9-8vc6

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-wrhw-j3f9-8vc6

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-wrhw-j3f9-8vc6

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# Patch Next advisory brief: CVE-2026-77244

Advisory: [mcp-atlassian] Authentication bypass in HTTP transport: AtlassianOpaqueTokenVerifier accepts any non-empty token
IDs: CVE-2026-77244, GHSA-wrhw-j3f9-8vc6
Record: https://patchnext.com/advisories/cve-2026-77244 (revision 3, 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: Critical (CVSS 10.0)
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-wrhw-j3f9-8vc6 (GitHub-reviewed advisory GHSA-wrhw-j3f9-8vc6 lists affected ranges: PyPI mcp-atlassian >=0 <0.22.0)
- Verified: https://osv.dev/vulnerability/GHSA-wrhw-j3f9-8vc6 (OSV record GHSA-wrhw-j3f9-8vc6 lists affected ranges: PyPI mcp-atlassian >=0 <0.22.0 (fixed))

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