Quick answers
- Is CVE-2026-86321 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-86321 being exploited in the wild.
- How severe is CVE-2026-86321?
- Medium severity, with a CVSS score of 5.3, published 7 September 2026.
- Which products and versions are affected?
- Java-Json-Tools Jackson-Coreutils 2.0.
- Is there a fix for CVE-2026-86321?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-86321 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-86321?
- Check whether you run Java-Json-Tools Jackson-Coreutils at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is a server-side request forgery (SSRF) combined with denial-of-service amplification via unsafe BigDecimal serialization. The JsonLoader.fromURL() method in src/main/java/com/github/fge/jackson/JsonLoader.java performs no scheme or hostname validation, accepting any URL including file:// URIs and internal IPs like 169.254.169.254. When combined with the default JacksonUtils configuration that enables WRITE_BIGDECIMAL_AS_PLAIN serialization, an attacker can serve a tiny JSON payload (e.g., {"x": 1e2000000000}) that expands to gigabytes in memory when deserialized and later serialized, causing OutOfMemoryError. The attack requires only network reachability and user control over URLs passed to fromURL(), with no authentication required. The vulnerability has been publicly disclosed with working proof-of-concept code and affects jackson-coreutils 2.0.
Affected products
- java-json-tools jackson-coreutils 2.0
Timeline
- 2026-07-28: disclosed
- 2026-09-07: advisory