CVE-2026-77272Public exploitNetwork attack vectorHinoki check available

Script execution via unescaped OAuth callback error

Published Sep 22, 2026 · Updated Sep 22, 2026

Reflected XSS in sooperset MCP Atlassian before 0.22.0 allows remote attackers to execute script via a crafted OAuth callback. The OAuth error parameter reaches CallbackHandler._send_response in oauth_setup.py and is interpolated into HTML without escaping. Exploitation requires the OAuth setup wizard to be running and a user to open the crafted callback from the local network, causing script execution in the callback page's browser context.

CVSS severity5.4
Medium
EPSS probability0.25%
Next 30 days · Oct 18, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Reflected XSS in sooperset MCP Atlassian before 0.22.0 allows remote attackers to execute script via a crafted OAuth callback. The OAuth error parameter reaches CallbackHandler._send_response in oauth_setup.py and is interpolated into HTML without escaping. Exploitation requires the OAuth setup wizard to be running and a user to open the crafted callback from the local network, causing script execution in the callback page's browser context.

The record

CVE
CVE-2026-77272
Published
Sep 22, 2026
Updated
Sep 22, 2026
Vendor
sooperset
Product
MCP Atlassian
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 22, 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=< 0.22.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

sooperset · MCP Atlassianversion=< 0.22.0

Published CVSS scores

5.4GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.001Malicious Link

Public exploit references

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

Technologies

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