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.
Metrics
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History
Tue, 29 Sep 2026 13:15:00 +0000
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threat_severity
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Tue, 22 Sep 2026 17:30:00 +0000
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ssvc
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Tue, 22 Sep 2026 15:00:00 +0000
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| Description | 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. | |
| Title | jackson-core: quadratic backtracking in NumberInput.PATTERN_FLOAT via looksLikeValidNumber() enables ReDoS | |
| Weaknesses | CWE-1333 CWE-400 |
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cvssV3_1
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Status: PUBLISHED
Assigner: HeroDevs
Published: 2026-09-22T14:53:20.999Z
Updated: 2026-09-22T15:52:44.881Z
Reserved: 2026-09-11T16:07:58.141Z
Link: CVE-2026-89407
Updated: 2026-09-22T15:52:32.473Z
Status : Deferred
Published: 2026-09-22T15:17:21.053
Modified: 2026-09-22T20:00:03.713
Link: CVE-2026-89407