Enables remote code execution via module overwrite in integrations used by Atlassian Confluence/Jira, impacting many enterprise deployments.
CVE-2026-77271
mcp-atlassian arbitrary write allows module overwrite and remote code execution.
Is CVE-2026-77271 being exploited?
Not confirmed. CVE-2026-77271 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.42% probability of exploitation in the next 30 days.
How severe is CVE-2026-77271?
CVE-2026-77271 is rated High with a CVSS score of 8.3. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-77271?
Yes. A fix has been recorded for CVE-2026-77271. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-77271 affect?
CVE-2026-77271 affects mcp-atlassian (<0.22.0), Atlassian Confluence integrations, Atlassian Jira integrations, Deployments using mcp-atlassian. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-77271?
Upgrade mcp-atlassian to >=0.22.0 and restrict upload/base_dir usage
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker-controlled attachment write can overwrite Python modules in app working dir, leading to remote code execution when imported.
Immediate action required
- affected< 0.22.0
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.