CVE-2026-59990 is a high-severity (CVSS 7.5) CWE-770 vulnerability in org.typelevel:jawn-parser_2.12. A fix is available for org.typelevel:jawn-parser_2.12 — see the affected versions and patch details below.
Jawn: Uncontrolled nesting depth in JSON parser
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-59990.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-59990 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,415 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
org.typelevel:jawn-parser_2.12☕org.typelevel:jawn-parser_2.13☕org.typelevel:jawn-parser_3Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.typelevel:jawn-parser_2.12 | all versions | 1.7.0org.typelevel:jawn-parser_2.12:1.7.0 |
| ☕Maven | org.typelevel:jawn-parser_2.13 | all versions | 1.7.0org.typelevel:jawn-parser_2.13:1.7.0 |
| ☕Maven | org.typelevel:jawn-parser_3 | all versions | 1.7.0org.typelevel:jawn-parser_3:1.7.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.typelevel:jawn-parser_2.12, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.typelevel:jawn-parser_2.12 to 1.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-59990 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is CVE-2026-59990 in your dependencies?
Find it across Maven, including transitive dependencies.