Neo4j: >> Neo4j >> 5.26.28 Security Vulnerabilities
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.
CVSS Score
5.5
EPSS Score
0.004
Published
2026-08-05
Insufficient escaping of unicode characters in query log in Neo4j Enterprise and Community editions prior to 2026.01 can lead to XSS if the user opens the logs in a tool that treats them as HTML. There is no security impact on Neo4j products, but this advisory is released as a precaution to treat the logs as plain text if using versions prior to 2026.01.
Proof of concept exploit: https://github.com/JoakimBulow/CVE-2026-1337
CVSS Score
1.1
EPSS Score
0.002
Published
2026-02-06