How severe is CVE-2026-77267?

No CVSS score has been assigned to CVE-2026-77267 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-77267?

CVE-2026-77267 affects the following packages: mcp-atlassian (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-77267?

Update mcp-atlassian to 0.22.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-77267 is resolved across your whole dependency graph.

How do I detect CVE-2026-77267 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mcp-atlassian, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-77267 if there is no patch (or I can't update yet)?

Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Is CVE-2026-77267 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-77267 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-77267?

CVE-2026-77267 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 21th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-77267?

CVE-2026-77267 is classified as Server-Side Request Forgery (SSRF) (CWE-918). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-77267 published, and has it been updated?

CVE-2026-77267 was published on September 22, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-77267 — mcp-atlassian

Fix: sooperset/mcp-atlassian@b041733

CVE-2026-77267 is a Server-Side Request Forgery (SSRF) vulnerability in mcp-atlassian. A fix is available for mcp-atlassian — see the affected versions and patch details below.

mcp-atlassian has an incomplete SSRF remediation

Also known asGHSA-5wf4-jqxh-8gm3PYSEC-2026-4084

Published

Sep 22, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-77267.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs21th percentile — riskier than 21% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍mcp-atlassian

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

The UserTokenMiddleware extracts URLs from X-Atlassian-Jira-Url and X-Atlassian-Confluence-Url HTTP headers and passes them directly to API client constructors without any SSRF validation.

Affected Package

Ecosystem: PyPI
Package: mcp-atlassian
Affected versions: all versions before fix commit 5cd697dfce91
Patched versions: >= commit 5cd697dfce91

Details

In main.py, _process_authentication_headers() extracts URLs from ASGI headers without validation. In dependencies.py, get_jira_fetcher() creates JiraConfig with url=jira_url_header directly. There is no validate_url call, no IP range check, no hostname validation.

The fix adds URL validation to some paths but the header-based URL extraction in _process_authentication_headers() still passes raw URLs through. The derived config objects use the header URL directly and the fetcher makes HTTP requests to that URL.

PoC

jira_url_header = headers.get(b"x-atlassian-jira-url")
jira_url_str = jira_url_header.decode("latin-1") if jira_url_header else None
service_headers["X-Atlassian-Jira-Url"] = jira_url_str

Steps to reproduce:

git clone https://github.com/sooperset/mcp-atlassian /tmp/mcp-atlassian_test
cd /tmp/mcp-atlassian_test && git checkout 5cd697dfce91~1
pip install -e .
python3 poc.py

Expected output:

VULNERABILITY CONFIRMED
User-supplied URLs from HTTP headers passed directly to JiraConfig/JiraFetcher with no SSRF validation

Impact

An attacker can set X-Atlassian-Jira-Url: http://169.254.169.254/latest/meta-data/ to access AWS instance metadata, or target any internal service. The server makes authenticated HTTP requests to the attacker-specified URL.

Suggested Remediation

Validate all user-supplied URLs against an allowlist of permitted hostnames or reject private/loopback/link-local IP ranges. Consider requiring server-side configuration of allowed Atlassian instance URLs.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`mcp-atlassian`	all versions	0.22.0`pip install --upgrade 'mcp-atlassian==0.22.0'`

Affected Products

1 product · 1 configurations

Application

mcp atlassianmcp-atlassian

< 0.22.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mcp-atlassian, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mcp-atlassian to 0.22.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-77267 is resolved across your whole dependency graph.
Workarounds
Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Frequently Asked Questions

### Summary The `UserTokenMiddleware` extracts URLs from `X-Atlassian-Jira-Url` and `X-Atlassian-Confluence-Url` HTTP headers and passes them directly to API client constructors without any SSRF validation. ### Affected Package - **Ecosystem:** PyPI - **Package:** mcp-atlassian - **Affected versions:** all versions before fix commit 5cd697dfce91 - **Patched versions:** >= commit 5cd697dfce91 ### Details In `main.py`, `_process_authentication_headers()` extracts URLs from ASGI headers without validation. In `dependencies.py`, `get_jira_fetcher()` creates `JiraConfig` with `url=jira_url_hea

O3 Security · Impact-Aware SCA

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