Neo4j Labs MCP Servers: SSRF and Data Modification via read_only Mode Bypass Through CALL Procedures

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2026-35402: 0.26% estimated exploitation activity in the next 30 days; percentile 18.33 (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 readonly mode in mcp-neo4j-cypher versions prior to 0.6.0 can be bypassed using CALL procedures. Details Impact The enforcing of readonly mode in vulnerable versions could be bypassed by certain APOC procedures. Patches v0.6.0 release hardened the checks around the mode. The only way to guarantee the server actions is to limit the permissions of the db credentials available to the server. Notes Impacts for server-side request forgery vulnerabilities may depend on both the configuration of the vulnerable system as well as the presence of other systems in the environment that could be accessed as part of exploitation. Recommended hardening - Limit the apoc procedures to what's required - Manage data loading privileges - Don't relax the default settings without compensating controls - apoc.import.file.enabled is false by default - apoc.import.file.useneo4jconfig is true by default to restrict file imports to the import folder Credits We want to publicly recognise the…

Published by the source

17 Apr 2026, 21:30 UTC

Last modified by the source

13 Jul 2026, 16:43 UTC

Source last checked

26 Oct 2026, 13:40 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-x3cv-r3g3-fpg9

2. Revision 2 · amended · 25 Oct 2026

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

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-x3cv-r3g3-fpg9

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# Patch Next advisory brief: CVE-2026-35402

Advisory: Neo4j Labs MCP Servers: SSRF and Data Modification via read_only Mode Bypass Through CALL Procedures
IDs: CVE-2026-35402, GHSA-x3cv-r3g3-fpg9
Record: https://patchnext.com/advisories/cve-2026-35402 (revision 3, source checked 26 Oct 2026, 13:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mcp-neo4j-cypher 0.6.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI mcp-neo4j-cypher: affected < 0.6.0; fixed in 0.6.0

## Suggested inspection (read-only)
- `python -m pip show mcp-neo4j-cypher`: 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-neo4j-cypher.
- 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://osv.dev/vulnerability/GHSA-x3cv-r3g3-fpg9 (OSV record GHSA-x3cv-r3g3-fpg9 lists affected ranges: PyPI mcp-neo4j-cypher >=0 <0.6.0 (fixed))
- Verified: https://github.com/advisories/GHSA-x3cv-r3g3-fpg9 (GitHub-reviewed advisory GHSA-x3cv-r3g3-fpg9 lists affected ranges: PyPI mcp-neo4j-cypher >=0 <0.6.0)

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