---
title: "CVE-2026-77244: [mcp-atlassian] Authentication bypass in HTTP transport: AtlassianOpaqueTokenVerifier accepts any non-empty token"
url: https://erroneo.us/security/cve/CVE-2026-77244/
description: "CVE-2026-77244 (mcp-atlassian (PyPI)): MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-09-22
date_modified: 2026-09-23
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-77244"
kev: false
cvss: 10
epss: 0.00286
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-77244: [mcp-atlassian] Authentication bypass in HTTP transport: AtlassianOpaqueTokenVerifier accepts any non-empty token

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.3% , percentile 20: FIRST’s model estimates a 0.3% chance of exploitation activity in the next 30 days, higher than 20% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes mcp-atlassian (PyPI) < 0.22.0, fixed in 0.22.0 . Check your lockfile, including transitive dependencies.

## What it is

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the HTTP transport accepts requests without a verified user identity and downstream fetcher construction falls back to the operator's globally configured Jira or Confluence credentials. A network client that can reach the MCP endpoint can invoke Atlassian tools as the operator, including read and write operations available to that account. The advisory traces the vulnerable input and processing flow through UserTokenMiddleware, AtlassianOpaqueTokenVerifier, getfetcher, and streamable-http, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

## Affected packages

- PyPI `mcp-atlassian` < 0.22.0 → fixed: 0.22.0

## Affected products (CVE record)

- sooperset mcp-atlassian: < 0.22.0

## Severity

- GitHub_M CVSS 3.1: 10 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N`
- GitHub CVSS 3.1: 10.0 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.29% probability of exploitation activity in the next 30 days; percentile 20.

## Sources

- [GitHub Advisory GHSA-wrhw-j3f9-8vc6](https://github.com/advisories/GHSA-wrhw-j3f9-8vc6)
- [CVE.org record CVE-2026-77244](https://www.cve.org/CVERecord?id=CVE-2026-77244)
- [NVD entry CVE-2026-77244](https://nvd.nist.gov/vuln/detail/CVE-2026-77244)
- [github.com](https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-wrhw-j3f9-8vc6)
- [github.com](https://github.com/sooperset/mcp-atlassian/pull/1448)
- [github.com](https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460)
- [github.com](https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0)

---
Source page: https://erroneo.us/security/cve/CVE-2026-77244/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt