GHSA-j3rv-43j4-c7qm is a high-severity (CVSS 8.1) CWE-184 vulnerability in com.fasterxml.jackson.core:jackson-databind. O3 Security confirms whether GHSA-j3rv-43j4-c7qm is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
jackson-databind has a PolymorphicTypeValidator bypass via generic type parameters that allows arbitrary class instantiation
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-j3rv-43j4-c7qm.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-j3rv-43j4-c7qm plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 358,265 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
com.fasterxml.jackson.core:jackson-databind☕com.fasterxml.jackson.core:jackson-databind☕com.fasterxml.jackson.core:jackson-databind☕tools.jackson.core:jackson-databindReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
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 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
BasicPolymorphicTypeValidatorconfigured with name-prefix allow rules. - Arbitrary class instantiation of any type assignable to the container's element/parameter position, with attacker-controlled property values (setter/field injection).
- Potential unauthenticated remote code execution when a class with exploitable side effects (JNDI lookup, JDBC/connection-pool gadgets,
TemplatesImpl-style loaders, etc.) is present on the classpath.
Applications that accept untrusted JSON and rely on a configured PTV — the documented, security-conscious configuration — are affected.
Proof of Concept
Configuration restricting polymorphic deserialization to a single safe container:
BasicPolymorphicTypeValidator ptv = BasicPolymorphicTypeValidator.builder()
.allowIfSubType("java.util.ArrayList")
.build();
ObjectMapper mapper = JsonMapper.builder()
.polymorphicTypeValidator(ptv)
.build();
Malicious payload (Wrapper.value is Object with @JsonTypeInfo(use = Id.CLASS, include = As.WRAPPER_ARRAY)):
{"value":["java.util.ArrayList<com.evil.EvilGadget>",[{"cmd":"calc.exe"}]]}
On vulnerable versions, com.evil.EvilGadget is instantiated and its cmd property is set, despite only java.util.ArrayList being allow-listed. On 2.18.8 / 2.21.4 / 3.1.4 the deserialization throws InvalidTypeIdException before instantiation.
Variant payloads (all bypass an ArrayList/HashMap allow-list):
| Type ID | Smuggled type position |
|---|---|
java.util.ArrayList<Evil> | list element |
java.util.HashMap<Evil,String> | map key |
java.util.HashMap<String,Evil> | map value |
java.util.ArrayList<java.util.ArrayList<Evil>> | nested element |
java.util.ArrayList<Evil[]> | array element |
Patches
Fixed in 2.18.8, 2.21.4 and 3.1.4 via the changes for FasterXML/jackson-databind#5988, commit 434d6c511. The fix adds recursive validation of each non-trivial type parameter (and array element types appearing as parameters) through the full PTV chain, with documented exemptions for Object (wildcard resolution) and Enum types.
PolymorphicTypeValidator was added in 2.10.0 so vulnerability N/A for versions prior to that.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | com.fasterxml.jackson.core:jackson-databind | ≥ 2.10.0&&< 2.18.8 | 2.18.8 |
| ☕Maven | com.fasterxml.jackson.core:jackson-databind | ≥ 3.0.0&&< 3.1.4 | 3.1.4 |
| ☕Maven | com.fasterxml.jackson.core:jackson-databind | ≥ 2.19.0&&< 2.21.4 | 2.21.4 |
| ☕Maven | tools.jackson.core:jackson-databind | ≥ 3.0.0&&< 3.1.4 | 3.1.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.fasterxml.jackson.core:jackson-databind. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update com.fasterxml.jackson.core:jackson-databind to 2.18.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-j3rv-43j4-c7qm is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-j3rv-43j4-c7qm is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-j3rv-43j4-c7qm. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability in `jackson-databind` is rated as Important. While it describes a potential bypass of the PolymorphicTypeValidator leading to arbitrary code execution, exploitation requires an attacker to already possess administrative privileges, specifically the `manage-realm` role. This flaw does not enable…
Frequently Asked Questions
Is GHSA-j3rv-43j4-c7qm in your dependencies?
O3 detects GHSA-j3rv-43j4-c7qm across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.