CVE-2026-27826Public exploit

Unauthenticated SSRF via unvalidated configuration headers

Published Mar 10, 2026 · Updated Mar 10, 2026

SSRF in MCP Atlassian before 0.17.0 allows remote attackers to reach internal services through unauthenticated HTTP configuration headers. UserTokenMiddleware accepts X-Atlassian-Jira-Url or X-Atlassian-Confluence-Url values, and dependency providers pass them into API client configurations without destination validation. Exploitation requires SSE or streamable HTTP transport and no Authorization header; successful requests expose internal services or cloud metadata and can inject attacker-controlled tool content.

CVSS severity8.2
High
EPSS probability13.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSRF in MCP Atlassian before 0.17.0 allows remote attackers to reach internal services through unauthenticated HTTP configuration headers. UserTokenMiddleware accepts X-Atlassian-Jira-Url or X-Atlassian-Confluence-Url values, and dependency providers pass them into API client configurations without destination validation. Exploitation requires SSE or streamable HTTP transport and no Authorization header; successful requests expose internal services or cloud metadata and can inject attacker-controlled tool content.

The record

CVE
CVE-2026-27826
Published
Mar 10, 2026
Updated
Mar 10, 2026
Vendor
sooperset
Product
MCP Atlassian
Classifications
CWE-918, CAPEC-664, T1190
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.17.0

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

sooperset · MCP Atlassianversion=< 0.17.0

Published CVSS scores

8.2GitHubCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
CAPEC-664Server Side Request Forgery
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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