jackson-databind has an array subtype allowlist bypass in BasicPolymorphicTypeValidator (allowIfSubTypeIsArray)

CVE-2026-54513 → View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

Description

Summary

BasicPolymorphicTypeValidator.Builder.allowIfSubTypeIsArray() allowlists any array type based only on clazz.isArray(), without validating the array's component (element) type against the configured allowlist. A PTV built with allowIfSubTypeIsArray() plus an explicit concrete-type allowlist therefore still permits EvilType[] even though EvilType is not allowlisted. When Jackson deserializes the elements and no per-element type IDs are present, it instantiates the component type directly with no further PTV check, bypassing the allowlist.

Impact

Applications using BasicPolymorphicTypeValidator with allowIfSubTypeIsArray() as a safeguard get no protection for concrete array component types; an attacker controlling JSON can instantiate non-allowlisted types via an array wrapper, re-opening the gadget-instantiation risk PTV is meant to prevent.

Affected / Patched (verified via git tag --contains)

  • 2.18 line: >= 2.10.0, < 2.18.8 -> fixed in 2.18.8
  • 2.19-2.21 line: >= 2.19.0, < 2.21.4 -> fixed in 2.21.4
  • 3.x line: >= 3.0.0, < 3.1.4 -> fixed in 3.1.4

PolymorphicTypeValidator was added in 2.10.0 so vulnerability N/A for versions prior to that.

Severity / CWE

Maintainer: significant. Reporter: HIGH. CWE-184 (Incomplete List of Disallowed Inputs); related CWE-502.

Upstream fix

FasterXML/jackson-databind#5981; fix PR #5983 (24529da), 2.18 backport PR #5984 (01d1692). Released 2026-06-04 in 2.18.8 / 2.21.4 / 3.1.4.

Credits

Omkhar Arasaratnam (@omkhar) - finder.

Basic information

Type
reviewed
Severity
high
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2026-06-23 21:22:15 UTC
Updated
2026-06-23 21:22:15 UTC
GitHub reviewed
2026-06-23 21:22:15 UTC

EPSS Score

Score Percentile
0.60% 43.97%

CVSS Scores

Base score Version Severity Vector
8.1 3.1 —
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.

Identifiers

Type Value
GHSA GHSA-rmj7-2vxq-3g9f ↗
CVE CVE-2026-54513 ↗

CWEs

CWE id Name
CWE-184 Incomplete List of Disallowed Inputs

Credits

  • omkhar (reporter)

Affected packages (4)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
maven com.fasterxml.jackson.core:jackson-databind >= 2.10.0, < 2.18.8 2.18.8 —
maven com.fasterxml.jackson.core:jackson-databind >= 2.19.0, < 2.21.4 2.21.4 —
maven com.fasterxml.jackson.core:jackson-databind >= 3.0.0, < 3.1.4 3.1.4 —
maven tools.jackson.core:jackson-databind >= 3.0.0, < 3.1.4 3.1.4 —

References

cvelogic Threat Intelligence