MCP Atlassian: Incomplete path traversal fix allows intra-CWD module overwrite and RCE (bypass of GHSA-xjgw-4wvw-rgm4)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N · score source

EPSS

• CVE-2026-77271: 0.60% estimated exploitation activity in the next 30 days; percentile 48.54 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The path traversal fix introduced in v0.17.0 (GHSA-xjgw-4wvw-rgm4) is incomplete. validatesafepath() is called without an explicit basedir, defaulting to os.getcwd(). In standard container deployments the process CWD is the application directory (e.g. /app), so paths within that directory, including the application's own Python source modules, pass validation without raising an exception. An attacker can overwrite a module file and achieve remote code execution on the next process restart. Versions = 0.17.0 are not fully patched as stated in the original advisory. Confirmed on v0.21.0 (latest). Details src/mcpatlassian/utils/io.py — validatesafepath() defaults to CWD when no basedir is supplied: Both call sites in src/mcpatlassian/confluence/attachments.py omit basedir: When the process CWD is /app, any path under /app satisfies isrelativeto(CWD) and passes the guard, including all Python source modules: PoC Prerequisites: same as GHSA-xjgw-4wvw-rgm4 — Confluence credentials…

Published by the source

22 Sep 2026, 20:36 UTC

Last modified by the source

1 Oct 2026, 17:56 UTC

Source last checked

26 Oct 2026, 13:54 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-6vmq-24h2-pj7j

2. Revision 3 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-6vmq-24h2-pj7j

4. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-6vmq-24h2-pj7j

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-77271

Advisory: MCP Atlassian: Incomplete path traversal fix allows intra-CWD module overwrite and RCE (bypass of GHSA-xjgw-4wvw-rgm4)
IDs: CVE-2026-77271, GHSA-6vmq-24h2-pj7j
Record: https://patchnext.com/advisories/cve-2026-77271 (revision 4, source checked 26 Oct 2026, 13:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mcp-atlassian 0.22.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI mcp-atlassian: affected < 0.22.0; fixed in 0.22.0

## Suggested inspection (read-only)
- `python -m pip show mcp-atlassian`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on mcp-atlassian.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6vmq-24h2-pj7j (GitHub-reviewed advisory GHSA-6vmq-24h2-pj7j lists affected ranges: PyPI mcp-atlassian >=0 <0.22.0)
- Verified: https://osv.dev/vulnerability/GHSA-6vmq-24h2-pj7j (OSV record GHSA-6vmq-24h2-pj7j lists affected ranges: PyPI mcp-atlassian >=0 <0.22.0 (fixed))

Commands are suggestions: review each one before running it.