CVE-2026-91776: jackson-databind: unbounded growth of the type id cache in TypeDeserializerBase retains every unknown raw type ID
FasterXML · jackson-databind
No fix listed · Affected: FasterXML jackson-databind · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 42% of scored CVEs
DescriptionCVE.org
TypeDeserializerBase._findDeserializer() in FasterXML jackson-databind caches the resolved deserializer under the raw, attacker-supplied type ID. When name-based polymorphism is configured with a fallback, for example @JsonTypeInfo(use = Id.NAME, defaultImpl = ...), every distinct unrecognized type ID resolves to the same fallback deserializer but is retained as its own key in the _deserializers map. That map has no configurable bound and lives for the lifetime of the type deserializer, so an attacker who can repeatedly supply fresh unknown type IDs causes monotonic memory retention across requests. The reporter observed 10,000 retained entries from 10,000 distinct unknown IDs, against a single entry for a control that repeated one unknown ID the same number of times, isolating attacker-controlled key cardinality from request volume. Exploitation requires an application that enables name-based polymorphism with a defaultImpl or equivalent fallback, accepts attacker-influenced type IDs, and reuses a long-lived ObjectMapper across requests. The fix stops caching fallback resolutions for unrecognized IDs and bounds both the number of cached entries and the length of a cacheable type ID.
Affected products2
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- FasterXML · jackson-databindfrom 2.0.0 up to and including 2.18.10; from 2.19.0 up to and including 2.21.6; from 2.22.0 up to and including 2.22.2
- FasterXML · jackson-databindfrom 3.0.0 up to and including 3.1.6; from 3.2.0 up to and including 3.2.2
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- FasterXML
- Published
- September 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-91776 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.