---
id: CVE-2026-89407
title: >-
  NumberInput.looksLikeValidNumber() in FasterXML jackson-core pre-validates
  "stringified numbers" with two regular expressions: PATTERN_FLOAT
  ([+-]?[0-9]*[\.]?[0-9]+([eE][+-]?[0-9]+)?), present since 2.17.0, and
  PATTERN_FLOAT_TRAILING_DOT…
summary: >-
  NumberInput.looksLikeValidNumber() in FasterXML jackson-core pre-validates
  "stringified numbers" with two regular expressions: PATTERN_FLOAT
  ([+-]?[0-9]*[\.]?[0-9]+([eE][+-]?[0-9]+)?), present since 2.17.0, and
  PATTERN_FLOAT_TRAILING_DOT…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-400
  - CWE-1333
vendor: FasterXML
product: 'com.fasterxml.jackson.core:jackson-core'
affected:
  - 'com.fasterxml.jackson.core:jackson-core >= 2.17.0 <= 2.18.10'
  - 'com.fasterxml.jackson.core:jackson-core >= 2.19.0 <= 2.21.6'
  - 'com.fasterxml.jackson.core:jackson-core >= 2.22.0 <= 2.22.2'
  - 'tools.jackson.core:jackson-core >= 3.0.0 <= 3.1.6'
  - 'tools.jackson.core:jackson-core >= 3.2.0 <= 3.2.1'
published: '2026-09-22'
updated: '2026-09-22'
sourceUpdated: '2026-09-22T20:00:03.713'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89407'
references:
  - url: 'https://github.com/FasterXML/jackson-core/issues/1649'
    label: 36c7be3b-2937-45df-85ea-ca7133ea542c
  - url: 'https://github.com/FasterXML/jackson-core/pull/1650'
    label: 36c7be3b-2937-45df-85ea-ca7133ea542c
  - url: 'https://github.com/FasterXML/jackson-core/pull/1701'
    label: 36c7be3b-2937-45df-85ea-ca7133ea542c
  - url: >-
      https://github.com/FasterXML/jackson-core/security/advisories/GHSA-p6pp-m3f8-5c89
    label: 36c7be3b-2937-45df-85ea-ca7133ea542c
  - url: >-
      https://github.com/FasterXML/jackson-core/security/advisories/GHSA-p6pp-m3f8-5c89
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-22T15:52:15.349840Z'
ingestedAt: '2026-09-22T15:05:01.076Z'
epss: 0.0063
epssPercentile: 0.48836
---

## Overview

NumberInput.looksLikeValidNumber() in FasterXML jackson-core pre-validates "stringified numbers" with two regular expressions: PATTERN_FLOAT ([+-]?[0-9]*[\.]?[0-9]+([eE][+-]?[0-9]+)?), present since 2.17.0, and PATTERN_FLOAT_TRAILING_DOT, added in 2.17.2. PATTERN_FLOAT places adjacent quantifiers over the same character class -- an optional [0-9]* run, an optional dot, then a required [0-9]+ run -- so input that ultimately fails to match forces Java's backtracking engine to retry every possible split point of the digit run. 



Matching cost therefore grows with the square of the input length. 



An attacker who can supply JSON that an application deserializes into a numeric target type reaches this method through jackson-databind's default String-to-number coercion (StdDeserializer and NumberDeserializers for BigDecimal, BigInteger, Double and Float). 



Because StreamReadConstraints.maxStringLength defaults to 20,000,000 characters, no constraint bounds the input before it reaches the regex. 



Testing by the reporter confirmed O(n^2) growth across five consecutive input-size doublings, with a single 160,000-character string consuming roughly 74 seconds in one call; a small number of concurrent requests of ordinary body size can therefore exhaust a server's request-handling thread pool. 



The affected method does not exist before 2.17.0, so 2.16.x and earlier releases are not affected. 



The fix replaces both regular expressions with a hand-rolled single-pass scan.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.