Description
The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service.



The synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses.



Root cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path.



Impact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up in O(n^2) BigInteger parsing, causing CPU-based denial of service.



No privileges or user interaction beyond the ability to submit data for parsing are required.



This issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.5 and from 2.19.0 through 2.21.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.0.x.



Versions prior to 2.15.0 are not affected, because StreamReadConstraints -- which defines the maxNumberLength setting -- was first introduced in jackson-core 2.15.0, so no such constraint exists to be bypassed in earlier releases. Note that GHSA-72hv-8253-57qq records the lower bound of the affected 2.x range as 2.0.0.
Published: 2026-08-04
Score: 6.9 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

The asynchronous JSON parser in jackson-core fails to enforce the maxNumberLength constraint, allowing an attacker to submit a number with arbitrary length. This defect causes unbounded memory allocation and, when large numbers are parsed as BigInteger or BigDecimal, can trigger O(n²) processing, exhausting CPU resources and potentially causing an OutOfMemoryError, leading to denial of service. No user privileges or interaction beyond the ability to send JSON data are required, making the attack vector trivial for any untrusted input stream.

Affected Systems

Affecting FasterXML:jackson-core versions 2.15.0 through 2.18.5 and 2.19.0 through 2.21.0, as well as tools.jackson.core:jackson-core 3.0.0 through 3.0.x. Versions earlier than 2.15.0 are unaffected because the StreamReadConstraints feature was introduced in 2.15.0.

Risk and Exploitability

The CVSS score of 6.9 indicates moderate severity. EPSS data is not available, and the vulnerability is not listed in CISA KEV, so the likelihood of widespread exploitation is currently unknown. However, because any component that uses the async parser can be exposed to untrusted JSON, the potential for denial of service remains significant if the affected versions are in production. The vulnerability exploits the inconsistent enforcement of number length across parsing APIs and can be triggered by any HTTP endpoint or messaging system that accepts JSON.

Generated by OpenCVE AI on August 4, 2026 at 19:48 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Apply a patched jackson-core release (any version newer than 2.21.0 or 3.0.x that includes the fix in PR 1555).
  • If an immediate upgrade is not possible, limit the length of incoming requests or implement a custom filter that rejects numbers exceeding a safe threshold before they reach the async parser.
  • Alternatively, temporarily switch the application to use the synchronous parser for all JSON payloads, where the length constraint is correctly enforced.

Generated by OpenCVE AI on August 4, 2026 at 19:48 UTC.

Tracking

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Advisories

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History

Tue, 11 Aug 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

threat_severity

Moderate

Tue, 04 Aug 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Tue, 04 Aug 2026 17:15:00 +0000

Type Values Removed Values Added
First Time appeared Fasterxml
Fasterxml jackson-core
Vendors & Products Fasterxml
Fasterxml jackson-core

Tue, 04 Aug 2026 15:00:00 +0000

Type Values Removed Values Added
Description The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service. The synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses. Root cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path. Impact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up in O(n^2) BigInteger parsing, causing CPU-based denial of service. No privileges or user interaction beyond the ability to submit data for parsing are required. This issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.5 and from 2.19.0 through 2.21.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.0.x. Versions prior to 2.15.0 are not affected, because StreamReadConstraints -- which defines the maxNumberLength setting -- was first introduced in jackson-core 2.15.0, so no such constraint exists to be bypassed in earlier releases. Note that GHSA-72hv-8253-57qq records the lower bound of the affected 2.x range as 2.0.0.
Title jackson-core: Number length constraint bypass in non-blocking (async) JSON parser leads to potential denial of service
Weaknesses CWE-770
References
Metrics cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N'}

Subscriptions

Fasterxml Jackson-core
cve-icon MITRE

Status: PUBLISHED

Assigner: HeroDevs

Published:

Updated: 2026-08-04T17:59:07.408Z

Reserved: 2026-07-30T15:20:53.701Z

Link: CVE-2026-18401

cve-icon Vulnrichment

Updated: 2026-08-04T17:58:52.981Z

cve-icon NVD

Status : Received

Published: 2026-08-04T15:16:29.900

Modified: 2026-08-04T19:16:43.657

Link: CVE-2026-18401

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-08-04T14:23:27Z

Links: CVE-2026-18401 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-08-04T20:00:05Z

Weaknesses
  • CWE-770

    Allocation of Resources Without Limits or Throttling