CVE-2026-68498: jackson-core: Delayed maxNameLength enforcement for char-backed input (ReaderBasedJsonParser) allows memory-exhaustion denial of service
StreamReadConstraints.maxNameLength (default 50,000 characters) is intended to bound how much memory a single JSON Object property name can consume while being parsed, independently of the much larger maxStringLength (default 100,000,000 characters) that bounds ordinary string values. For parsers built over character input — Reader, String or char[] sources, all served by ReaderBasedJsonParser — that bound is not applied while the name is being accumulated. The code path instead re-uses the string-value length check, which is roughly 2000x larger by default.
In the character-input slow path, ReaderBasedJsonParser.parseName2() accumulates the name into the TextBuffer and, when a segment fills, calls TextBuffer.finishCurrentSegment(), which validates only maxStringLength. The correct check, StreamReadConstraints.validateNameLength(int), is reached afterwards in CharsToNameCanonicalizer.findSymbol(), once the entire name has been scanned to its closing quote. By that point the full name — up to maxStringLength characters — has already been buffered in memory.
A remote attacker who can have a single sufficiently long JSON Object property name parsed through this path can force allocation on the order of 100,000,000 characters (approximately 200 MB, with segment bookkeeping pushing real peak usage higher) before any StreamConstraintsException is thrown, instead of the approximately 50,000-character (about 100 KB) bound the API promises. Repeating this across concurrent requests can exhaust the heap and crash the process. No authentication or user interaction is required. Because StreamReadConstraints.maxDocumentLength is disabled by default (-1), nothing else bounds the token first, so the issue is exploitable under default configuration.
Byte-input parsers are not affected: UTF8StreamJsonParser, UTF8DataInputJsonParser and the non-blocking (async) parsers re-validate maxNameLength on every growth of the name-decode buffer via ParserBase.growNameDecodeBuffer(), rejecting an oversized name after allocating only tens of kilobytes. Applications are exposed when untrusted JSON is parsed from a String, Reader or char[] — for example an HTTP request body already read into a String — rather than from raw UTF-8 bytes.
This issue affects com.fasterxml.jackson.core:jackson-core from 2.16.0 and tools.jackson.core:jackson-core from 3.0.0. Releases before 2.16.0 are not affected, because StreamReadConstraints.maxNameLength was first introduced in jackson-core 2.16.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
Parse untrusted JSON from raw UTF-8 byte input using byte-input parsers instead of String, Reader, or char[] sources, because UTF8StreamJsonParser, UTF8DataInputJsonParser, and non-blocking parsers re-validate maxNameLength during buffer growth.
Event History
Frequently Asked Questions
Which applications are exposed to this denial-of-service condition?
Applications are exposed when they parse attacker-controlled JSON from Reader, String, or char[] sources, because those inputs use ReaderBasedJsonParser. An attacker must be able to submit a JSON object containing a sufficiently long property name.
Are default constraint settings sufficient to prevent the issue?
No. The default maxNameLength is 50,000 characters, but the affected character-input path accumulates names using the much larger maxStringLength limit, which defaults to 100,000,000 characters. The name-length validation occurs only after the full property name has already been buffered.
What is the impact of successful exploitation?
A remote unauthenticated attacker can cause excessive memory allocation by supplying a single very long JSON object property name. This can lead to memory-exhaustion denial of service.