CVE-2026-89407

jackson-core: quadratic backtracking in NumberInput.PATTERN_FLOAT via looksLikeValidNumber() enables ReDoS

CVSS 3.1 7.5 HIGHCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-89407

Published

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.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-89407

Published

com.fasterxml.jackson.core:jackson-core

https://repo1.maven.org/maven2

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "FasterXML",
                    "product": "jackson-core",
                    "collectionURL": "https://repo1.maven.org/maven2",
                    "packageName": "com.fasterxml.jackson.core:jackson-core",
                    "repo": "https://github.com/FasterXML/jackson-core",
                    "programRoutines": [
                        {
                            "name": "com.fasterxml.jackson.core.io.NumberInput.looksLikeValidNumber"
                        }
                    ],
                    "versions": [
                        {
                            "status": "affected",
                            "version": "2.17.0",
                            "lessThanOrEqual": "2.18.10",
                            "versionType": "maven"
                        },
                        {
                            "status": "affected",
                            "version": "2.19.0",
                            "lessThanOrEqual": "2.21.6",
                            "versionType": "maven"
                        },
                        {
                            "status": "affected",
                            "version": "2.22.0",
                            "lessThanOrEqual": "2.22.2",
                            "versionType": "maven"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }

tools.jackson.core:jackson-core

https://repo1.maven.org/maven2

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "FasterXML",
                    "product": "jackson-core",
                    "collectionURL": "https://repo1.maven.org/maven2",
                    "packageName": "tools.jackson.core:jackson-core",
                    "repo": "https://github.com/FasterXML/jackson-core",
                    "programRoutines": [
                        {
                            "name": "tools.jackson.core.io.NumberInput.looksLikeValidNumber"
                        }
                    ],
                    "versions": [
                        {
                            "status": "affected",
                            "version": "3.0.0",
                            "lessThanOrEqual": "3.1.6",
                            "versionType": "maven"
                        },
                        {
                            "status": "affected",
                            "version": "3.2.0",
                            "lessThanOrEqual": "3.2.1",
                            "versionType": "maven"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }

Original source record · Cite this exact observation · Complete original publisher JSON