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Advisory record · GHSA-g5xv-mhgm-v5f6

MCP Atlassian: OAuth fallback token storage writes plaintext access and refresh tokens with group-readable permissions

CVSS 6.1 MediumEPSS 0.0011 · 1st percentile

Published by the GitHub Advisory Database at 22 Sept 2026, 20:36 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
mcp-atlassianPyPI<0.22.00.22.0
Identifiers
GHSA-g5xv-mhgm-v5f6 · CVE-2026-77250 · PYSEC-2026-4094
Weakness (CWE)
CWE-312
Tags
Published
22 Sept 2026
Updated
1 Oct 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

MCP Atlassian versions before 0.22.0 always write a plaintext fallback copy of OAuth access and refresh tokens to a file under the user's home directory, created with default permissions (observed as mode 0664). A local user in the same group, or any process that can read the home directory, could read these tokens and use them for continued Atlassian API access. Upgrade to mcp-atlassian 0.22.0 or later; the source lists no workaround.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
6.1 Medium 3.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0011, the 1st percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:09 UTC First seen by agentprime
  2. 31 Oct 2026, 14:09 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.