CVE-2026-104182: stream-json: JSONC parser and verifier re-scan the whole accumulated comment on every input chunk
stream-json is a micro-library of stream components for processing JSON and JSONC with a minimal memory footprint. Prior to 3.6.0, the JSONC parser at stream-json/jsonc/parser.js and verifier at stream-json/jsonc/verifier.js restart comment-terminator scanning from the opening slash whenever a block or line comment spans an input chunk, while retaining the accumulated comment buffer. Delivering a large valid comment across many small chunks therefore causes quadratic CPU work and can stall the Node.js event loop. The maintainer characterizes the attack vector as local because the documented JSONC input is locally owned or user-controlled configuration, rather than input intended for the open internet. This JSONC-only scope does not include the plain JSON parser, which advances through and discards consumed string and number data. This issue is fixed in version 3.6.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
stream-jsonto a version that resolves this vulnerability.Fixed in 3.6.0
Event History
Frequently Asked Questions
Which uses of stream-json are affected?
Only the JSONC parser and verifier are affected when comments span input chunks. The plain JSON parser is not affected.
What does exploitation require?
An attacker or local user must be able to provide JSONC input containing a large valid block or line comment delivered in many small chunks. This causes repeated rescanning of the accumulated comment and can stall the Node.js event loop.
Are applications that only process remotely supplied JSON exposed?
The maintainer characterizes the attack vector as local because documented JSONC input is locally owned or user-controlled configuration, not input intended for the open internet. Exposure therefore depends on whether untrusted parties can influence JSONC configuration or otherwise control chunked JSONC input.
What should be done if the issue is relevant?
Upgrade stream-json to version 3.6.0, which fixes the issue. If upgrading is not immediately possible, avoid processing large JSONC comments from untrusted or user-controlled sources, especially when input can arrive in many small chunks.