Denial of service via unchecked async number length
Published Aug 4, 2026 · Updated Aug 4, 2026
Resource exhaustion in FasterXML Jackson Core's async JSON parser allows remote attackers to exhaust service resources with long number tokens. NonBlockingUtf8JsonParserBase accumulates digits in TextBuffer and finalizes tokens without invoking the integer or floating-point length validators. Exposure requires attacker-controlled JSON to reach the non-blocking API; oversized numbers exhaust memory, and numeric conversion also consumes excessive CPU.
Summary
What happened
Resource exhaustion in FasterXML Jackson Core's async JSON parser allows remote attackers to exhaust service resources with long number tokens. NonBlockingUtf8JsonParserBase accumulates digits in TextBuffer and finalizes tokens without invoking the integer or floating-point length validators. Exposure requires attacker-controlled JSON to reach the non-blocking API; oversized numbers exhaust memory, and numeric conversion also consumes excessive CPU.
The record
- CVE
- CVE-2026-18401
- Published
- Aug 4, 2026
- Updated
- Aug 4, 2026
- Vendor
- FasterXML
- Product
- Jackson Core
- Classifications
- CWE-770, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 4, 2026CVE publishedPublication date reported by the CVE source.
- Aug 4, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2.15.0 <=2.18.5
- Affected versionversion=2.19.0 <2.21.1
- Affected versionversion=3.0.0 <3.1.0
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- JUnit proof of concept for async number-length bypassproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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