CVE-2026-89425: Fasterxml Jackson-Core

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

UTF8DataInputJsonParser._reportInvalidToken() in FasterXML jackson-core builds the offending-token text for its error message by appending Java identifier characters to a StringBuilder in a loop that has no upper bound. Unlike the three sibling parser implementations, including UTF8StreamJsonParser, it never consults ErrorReportConfiguration.getMaxErrorTokenLength() (default 256). A malformed token supplied to a parser created through JsonFactory.createParser(DataInput) is therefore accumulated in full. No StreamReadConstraints setting mitigates this: maxDocumentLength cannot be applied to DataInput sources at all, and maxStringLength does not cover this path because the accumulation bypasses ReadConstrainedTextBuffer. The reporter measured a 20,000,109-character exception message from a 20-million-character malformed token on the DataInput path, against 367 characters for identical input on the InputStream path. Scaling the payload drives the StringBuilder, which also incurs byte-to-char expansion and internal array doubling, to many times the raw payload size and can trigger OutOfMemoryError for the whole JVM. UTF8DataInputJsonParser was introduced in 2.8.0 together with createParser(DataInput); releases before 2.8.0 do not contain the affected class.

Affected products

• Fasterxml Jackson-Core: from 2.8.0, up to and including 2.18.10; from 2.19.0, up to and including 2.21.6; from 2.22.0, up to and including 2.22.2; from 3.0.0, up to and including 3.1.6; from 3.2.0, up to and including 3.2.2

Published 2026-09-23. Last modified 2026-09-24.