CVE-2026-77268

MEDIUMPre-NVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1% (1st percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
5.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.1%CVSS: 5.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the OAuth fallback token directory and JSON file are created without explicit owner-only modes. Local users or processes with access through the resulting group or world permission bits can read access and refresh tokens and reuse the associated Atlassian session. The advisory traces the vulnerable input and processing flow through ~/.mcp-atlassian, oauth-.json, access_token, and refresh_token, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

CVSS v3
5.5
EG Score
5.5MEDIUMmedium confidence
EG Risk
25
EG Risk 25/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity55% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.1%
EPSS %ILE
1st
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 22, 2026

Last Modified

September 29, 2026

Advisory Details (4)

Auto-updated Sep 22, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available

v0.22.0

Patch available: sooperset/mcp-atlassian v0.22.0

https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0
github_commit Patch Available

commit b041733473f9 (sooperset/mcp-atlassian)

Patch available: sooperset/mcp-atlassian v0.22.0 (contains commit b041733473f9)

https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460
github_pr Patch Available

Security hardening across attachment, transport, SSRF, authorization, filter, and OAuth layers

Patch available: sooperset/mcp-atlassian v0.22.0 (PR #1448 merged 2026-07-10)

https://github.com/sooperset/mcp-atlassian/pull/1448
github Patch Available🟡 PoC Available

Insecure File Permissions on OAuth Token Storage · Advisory · sooperset/mcp-atlassian · GitHub

https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-4596-2p6p-28cv

Vendor Advisories for CVE-2026-77268(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
mcp-atlassian0.1.1 ... 0.9.0 (79 versions)0.22.0—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 20× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-03 17:22 UTCEG score recompute
  2. 2026-10-03 14:26 UTCEPSS rescore
  3. 2026-10-02 17:53 UTCEG score recompute
  4. 2026-10-01 19:50 UTCEPSS rescore
  5. 2026-09-30 18:49 UTCEG score recompute
  6. 2026-09-29 16:48 UTCEG score recompute
  7. 2026-09-27 17:21 UTCEG score recompute
  8. 2026-09-27 13:48 UTCEPSS rescore
  9. 2026-09-26 17:52 UTCEG score recompute
  10. 2026-09-26 15:59 UTCEPSS rescore
  11. 2026-09-26 00:28 UTCEPSS rescore
  12. 2026-09-24 17:59 UTCEG score recompute
  13. 2026-09-24 14:04 UTCEPSS rescore
  14. 2026-09-23 18:26 UTCEG score recompute
  15. 2026-09-23 17:54 UTCEPSS rescore
  16. 2026-09-23 15:20 UTCEG score recompute
  17. 2026-09-23 14:50 UTCEG score recompute
  18. 2026-09-22 19:37 UTCEG score recompute
  19. 2026-09-22 18:53 UTCEG score recompute
  20. 2026-09-22 18:53 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-77268?
CVE-2026-77268 is a medium vulnerability published on September 22, 2026. MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the OAuth fallback token directory and JSON file are created without explicit owner-only modes. Local users or processes with access through the resulting group or world permission…
When was CVE-2026-77268 disclosed?
CVE-2026-77268 was first published on September 22, 2026, with the most recent update on September 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-77268 actively exploited?
CVE-2026-77268 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.1% probability of exploitation in the next 30 days (1st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-77268?
CVE-2026-77268 has a CVSS base score of 5.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-77268?
A fix for CVE-2026-77268 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-77268 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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