CVE-2026-77256Hinoki check available

OAuth token disclosure via permissive backup permissions

Published Sep 22, 2026 · Updated Sep 22, 2026

Information disclosure in sooperset MCP Atlassian before 0.22.0 allows local users to read plaintext OAuth access and refresh tokens. OAuthConfig._save_tokens_to_file writes the fallback token file using permissions inherited from the process umask instead of forcing an owner-only mode. Exposure requires fallback-file storage and a group- or world-readable umask, and a stolen refresh token preserves Atlassian access.

CVSS severityUnavailable
Unscored
EPSS probability0.35%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Information disclosure in sooperset MCP Atlassian before 0.22.0 allows local users to read plaintext OAuth access and refresh tokens. OAuthConfig._save_tokens_to_file writes the fallback token file using permissions inherited from the process umask instead of forcing an owner-only mode. Exposure requires fallback-file storage and a group- or world-readable umask, and a stolen refresh token preserves Atlassian access.

The record

CVE
CVE-2026-77256
Published
Sep 22, 2026
Updated
Sep 22, 2026
Vendor
sooperset
Product
MCP Atlassian
Classifications
T1552.001
Attack vector
local
Privileges
authenticated

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 vectorlocal
Required privilegesauthenticated

What is affected?

sooperset · MCP Atlassianversion=< 0.22.0

Published CVSS scores

No CVSS assessment is available in this record.

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1552.001Unsecured Credentials: Credentials In Files

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

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