CVE-2026-59990

The Jawn parser before 1.6.1 is vulnerable to a denial of service attack via untrusted input.

Impact

A remote attacker who can submit JSON to any jawn-backed parse method can exhaust JVM heap and trigger java.lang.OutOfMemoryError. This is treated by Scala as a fatal error and not typically handled by scala.util.Try or cats.effect.IO.

Patches

Version 1.6.1 introduces a configurable nesting-depth limit (Parser#maxDepth, default 4096). Inputs deeper than the limit fail with a recoverable ParseException instead of exhausting heap.

Users who require deeper nesting may override maxDepth on a Parser subclass.

Workarounds

• Enforce an input size limit small enough that the resulting context stack cannot exhaust heap, (e.g. http4s EntityLimiter).
• Pre-scan untrusted input and reject documents whose maximum delimiter nesting exceeds a threshold before handing them to jawn.