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
Weakness
The product constructs a log message from external input, but it does not neutralize or incorrectly neutralizes special elements when the message is written to a log file.
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/268.html
- https://cwe.mitre.org/data/definitions/81.html
- https://cwe.mitre.org/data/definitions/93.html