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CVE-2026-77261· NVD / CVE Program· CNA GitHub_M

MCP Atlassian: SSRF redirect protection missing for basic-auth and OAuth authentication branches

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, _make_ssrf_safe_hook is omitted from JiraFetcher and ConfluenceFetcher sessions created through the basic-auth and oauth_pat branches. If an attacker-controlled or compromised configured Atlassian instance returns a redirect to an internal address, those sessions can follow the redirect without revalidating its destination. This issue is fixed in version 0.22.0.

HighCVSS 8.5 · v3.1—No exploit Fix available
Published
Sep 22, 2026
Updated
Sep 25, 2026
EPSS
0.3% · 23th percentile
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Report tools

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Action score

34

Monitor

Low priority for now.

CVSS
34 / 40 · 8.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
8.5
CNA · GitHub_M
7.1
1.4 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

VendorProduct
mcp-atlassianmcp atlassian

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • mcp-atlassian mcp atlassianbefore 0.22.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • sooperset mcp-atlassian

    • < 0.22.0affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
PyPImcp-atlassianbefore 0.22.00.22.0

Same product

mcp-atlassian: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-77244[mcp-atlassian] Authentication bypass in HTTP transport: AtlassianOpaqueTokenVerifier accepts any non-empty token
    40Plan
  • CVE-2026-77254MCP Atlassian: Unauthenticated HTTP MCP requests can use globally configured Jira and Confluence credentials
    36Monitor
  • CVE-2026-77243MCP Atlassian: ENABLED_TOOLS / Toolset authorization bypass
    35Monitor
  • CVE-2026-77274MCP Atlassian: SSRF Protection Bypass
    35Monitor
  • CVE-2026-77262MCP Atlassian: Path Traversal / Arbitrary File Read in confluence_upload_attachment MCP tool (incomplete fix of CVE-2026-27825)
    34Monitor
  • CVE-2026-77255MCP Atlassian: Arbitrary File Read & Exfiltration (Confused Deputy) in JIRA update_issue
    34Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
sooperset mcp-atlassian0.22.0 · descriptionVendor (CNA)
PyPI:mcp-atlassian0.22.0Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-772740 days apartMCP Atlassian: SSRF Protection Bypass
    35Monitor
  • CVE-2026-772670 days apartmcp-atlassian has an incomplete SSRF remediation
    33Monitor
  • CVE-2026-772650 days apartMCP Atlassian: SSRF via DNS Rebinding in Header-Based Authentication Flow
    30Monitor
  • CVE-2026-772490 days apartMCP Atlassian: Incomplete fix for CVE-2026-27826: redirect-based SSRF via unhooked requests session in Jira user-permission lookup
    21Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

  • CVE-2026-772540 days apartMCP Atlassian: Unauthenticated HTTP MCP requests can use globally configured Jira and Confluence credentials
    36Monitor
  • CVE-2026-772420 days apartMCP Atlassian: Incomplete fix for CVE-2026-27826: DNS rebinding bypasses SSRF validation (validated IP not pinned)
    30Monitor

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
low · data or configuration can be modified
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality impact
High
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-918 · Server-Side Request Forgery (SSRF)

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Noroxi analysis

No Noroxi analysis for this record yet

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Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records