CVE-2026-18401
Description
A flaw was found in jackson-core. The non-blocking (asynchronous) JSON parser does not properly enforce the maximum number length constraint. A remote attacker can exploit this by submitting a specially crafted JSON document containing an arbitrarily long number to an application using the asynchronous parser. This can lead to excessive memory allocation and CPU exhaustion, resulting in a denial of service (DoS) for the affected application.
Statement
Red Hat's assessment of this vulnerability differs from the reported vendor severity. The flaw exists only in jackson-core's non-blocking (asynchronous) JSON parser, which does not enforce the maxNumberLength constraint defined by StreamReadConstraints. Applications that use the standard, synchronous parsing API (the default for the vast majority of Java applications using jackson-core, including via ObjectMapper) enforce this limit correctly and are not affected by this specific code path. Only applications that explicitly invoke the non-blocking parser API, typically reactive frameworks processing untrusted network input, are exposed to the described memory/CPU exhaustion behavior. Red Hat rates this issue as Moderate.
Mitigation
No mitigation is available for applications that use the non-blocking/async parser API with untrusted input. Affected users should upgrade to jackson-core 2.18.6, 2.21.1, 3.1.0, or later. Applications that only use the standard (synchronous) parser API are not affected and require no action.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | None | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | Low | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource. It can be easy for an attacker to consume many resources by rapidly making many requests or causing larger resources to be used than is needed.
Frequently Asked Questions
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