Externally Controlled Format String in Scripting Functions

The rquickjs crate used by SurrealDB implements Rust bindings to the QuickJS C library and is used to execute SurrealDB scripting functions. The rquickjs function Exception::throw_type takes a string and returns an error object. Prior to version 0.4.2 of the crate, this string would be fed directly into printf, which will receive the error string as a format string with no additional arguments, leading to undefined behavior. This issue triggers when a SurrealDB scripting function returns an error and its input contains a format string such as %s or %d.

This vulnerability can only affect SurrealDB servers explicitly enabling the scripting capability with --allow-scripting or --allow-all and equivalent environment variables SURREAL_CAPS_ALLOW_SCRIPT=true and SURREAL_CAPS_ALLOW_ALL=true.

Impact

An attacker with privileges to execute scripting functions with arbitrary inputs may be able to exploit this format string vulnerability in order read arbitrary memory from the remote SurrealDB process. A format string vulnerability may also be further exploited to execute arbitrary code with the privileges of the SurrealDB process.

The fact that error messages are limited to 256 bytes coupled with exploit mitigation features supported in Rust executables may somewhat increase the complexity of exploiting this vulnerability to reliably achieve remote code execution in practice.…