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CVE-2026-77267

mcp-atlassian has an incomplete SSRF remediation

8.3 HighFix available

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the X-Atlassian-Jira-Url and X-Atlassian-Confluence-Url headers are processed by _process_authentication_headers and used to construct Atlassian fetchers without calling validate_url_for_ssrf. A caller who can set these headers can supply an internal or metadata-service URL and cause the server to send requests to that destination, bypassing the incomplete CVE-2026-27826 remediation. This issue is fixed in version 0.22.0.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
None
Availability
None

Exploit likelihood

0.32%Down 0.3 points since Sep 23, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.3

mcp-atlassian has an incomplete SSRF remediation

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the X-Atlassian-Jira-Url and X-Atlassian-Confluence-Url headers are processed by _process_authentication_headers and used to construct Atlassian fetchers without calling validate_url_for_ssrf. A caller who can set these headers can supply an internal or metadata-service URL and cause the server to send requests to that destination, bypassing the incomplete CVE-2026-27826 remediation. This issue is fixed in version 0.22.0.

Record
CVE-2026-77267
CVSS 4.0
8.3 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
Weakness
CWE-918
Updated
2026-11-02
EUVDEUVD-2026-84621 8.3

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the X-Atlassian-Jira-Url and X-Atlassian-Confluence-Url headers are processed by _process_authentication_headers and used to construct Atlassian fetchers without calling validate_url_for_ssrf. A caller who can set these headers can supply an internal or metadata-service URL and cause the server to send requests to that destination, bypassing the incomplete CVE-2026-27826 remediation. This issue is fixed in version 0.22.0.

Record
EUVD-2026-84621
CVSS 4.0
8.3 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-5wf4-jqxh-8gm3 8.3

mcp-atlassian has an incomplete SSRF remediation

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:

  1. git clone https://github.com/sooperset/mcp-atlassian /tmp/mcp-atlassian_test
  2. cd /tmp/mcp-atlassian_test && git checkout 5cd697dfce91~1
  3. pip install -e .
  4. 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.

Record
GHSA-5wf4-jqxh-8gm3
CVSS 4.0
8.3 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
Weakness
CWE-918
Updated
2026-11-02
NVD 8.3

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the X-Atlassian-Jira-Url and X-Atlassian-Confluence-Url headers are processed by _process_authentication_headers and used to construct Atlassian fetchers without calling validate_url_for_ssrf. A caller who can set these headers can supply an internal or metadata-service URL and cause the server to send requests to that destination, bypassing the incomplete CVE-2026-27826 remediation. This issue is fixed in version 0.22.0.

Record
CVE-2026-77267
CVSS 4.0
8.3 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-918
Updated
2026-11-02
OSV 8.3

mcp-atlassian has an incomplete SSRF remediation

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the X-Atlassian-Jira-Url and X-Atlassian-Confluence-Url headers are processed by _process_authentication_headers and used to construct Atlassian fetchers without calling validate_url_for_ssrf. A caller who can set these headers can supply an internal or metadata-service URL and cause the server to send requests to that destination, bypassing the incomplete CVE-2026-27826 remediation. This issue is fixed in version 0.22.0.

Record
CVE-2026-77267
CVSS 4.0
8.3 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
Weakness
CWE-918
Updated
2026-11-02
OSVGHSA-5wf4-jqxh-8gm3 8.3

mcp-atlassian has an incomplete SSRF remediation

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:

  1. git clone https://github.com/sooperset/mcp-atlassian /tmp/mcp-atlassian_test
  2. cd /tmp/mcp-atlassian_test && git checkout 5cd697dfce91~1
  3. pip install -e .
  4. 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.

Record
GHSA-5wf4-jqxh-8gm3
CVSS 4.0
8.3 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
Weakness
CWE-918
Updated
2026-11-02
OSVPYSEC-2026-4084 8.3

mcp-atlassian has an incomplete SSRF remediation

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:

  1. git clone https://github.com/sooperset/mcp-atlassian /tmp/mcp-atlassian_test
  2. cd /tmp/mcp-atlassian_test && git checkout 5cd697dfce91~1
  3. pip install -e .
  4. 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.

Record
PYSEC-2026-4084
CVSS 4.0
8.3 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
mcp-atlassian
PyPI
 before 0.22.0
0.22.0
mcp-atlassian
PyPI
 before 0.22.0, plus listed versions
0.1.10.1.100.1.110.1.120.1.13
Show 45 moreShow less
0.1.140.1.150.1.160.1.20.1.30.1.40.1.60.1.70.1.80.1.90.10.00.10.10.10.20.10.30.10.40.10.50.10.60.11.00.11.10.11.100.11.110.11.120.11.20.11.2a20.11.30.11.40.11.50.11.60.11.70.11.80.11.90.12.00.13.00.13.10.14.00.14.10.14.20.14.30.15.00.16.00.16.10.17.00.18.00.18.10.19.0
0.22.0

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-77267 is a high vulnerability (CVSS 8.3) in Mcp-atlassian Mcp Atlassian, published September 22, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.32%, the 25th percentile. Fixed in mcp-atlassian 0.22.0.

References

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Left out here: 29 versions. The JSON record has them.

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