jackson-databind has a PolymorphicTypeValidator bypass via generic type parameters that allows arbitrary class instantiation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.1 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-54512: 1.07% estimated exploitation activity in the next 30 days; percentile 64.80 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

`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 ` ` 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 is the same vulnerability class responsible for the historical sequence of jackson-databind deserialization CVEs; here it manifests as a validator bypass rather than a missing deny-list entry.

Impact - Bypass of the PTV allow-list, including the recommended `BasicPolymorphicTypeValidator` configured with name-prefix allow rules. - Arbitrary class instantiation of any type assignable to the container's element/parameter position, with…

Published by the source

23 Jun 2026, 21:21 UTC

Last modified by the source

28 Oct 2026, 10:56 UTC

Source last checked

29 Oct 2026, 06:45 UTC

1. Revision 2 · amended · 29 Oct 2026

   Amended from osv record GHSA-j3rv-43j4-c7qm

2. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-j3rv-43j4-c7qm

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# Patch Next advisory brief: CVE-2026-54512

Advisory: jackson-databind has a PolymorphicTypeValidator bypass via generic type parameters that allows arbitrary class instantiation
IDs: CVE-2026-54512, GHSA-j3rv-43j4-c7qm
Record: https://patchnext.com/advisories/cve-2026-54512 (revision 2, source checked 29 Oct 2026, 06:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: tools.jackson.core:jackson-databind 3.1.4; com.fasterxml.jackson.core:jackson-databind 3.1.4, 2.21.4, 2.18.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven tools.jackson.core:jackson-databind: affected >= 3.0.0, < 3.1.4; fixed in 3.1.4
- Maven com.fasterxml.jackson.core:jackson-databind: affected >= 2.10.0, < 2.18.8; >= 3.0.0, < 3.1.4; >= 2.19.0, < 2.21.4; fixed in 2.21.4, 2.18.8, 3.1.4

## Suggested inspection (read-only)
- Maven tools.jackson.core:jackson-databind: check the installed version with your package manager.
- Maven com.fasterxml.jackson.core:jackson-databind: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on tools.jackson.core:jackson-databind, com.fasterxml.jackson.core:jackson-databind.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-j3rv-43j4-c7qm (GitHub-reviewed advisory GHSA-j3rv-43j4-c7qm lists affected ranges: Maven com.fasterxml.jackson.core:jackson-databind >=2.10.0 =3.0.0 =2.19.0 =3.0.0 <=3.1.3)
- Verified: https://osv.dev/vulnerability/GHSA-j3rv-43j4-c7qm (OSV record GHSA-j3rv-43j4-c7qm lists affected ranges: Maven com.fasterxml.jackson.core:jackson-databind >=2.10.0 =3.0.0 =2.19.0 =3.0.0 <3.1.4 (fixed))

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