CVE-2026-71429: stream-json: pick/ignore/filter/replace filters are O(depth²) on nested input — small crafted JSON blocks the event loop for seconds→minutes (DoS)

Vulnerability summary

CVE-2026-71429 is a medium (CVSS 6.2) Inefficient Algorithmic Complexity vulnerability in uhop stream-json. EPSS estimates a 0.16% chance of exploitation in the next 30 days, higher than 5.2% of scored vulnerabilities.

Timeline

1. 03-09-2026
   PublishedVulnerability first disclosed.
2. 04-09-2026
   Last modifiedVulnerability information updated.

Description

stream-json is a micro-library of stream components for processing JSON and JSONC with a minimal memory footprint. Prior to 3.5.0, the path filters pick, ignore, filter, and replace in src/core/filters/filter-base.js recompute the full path string from the nesting stack for every checkable token. Because the stack length equals the current nesting depth and a checkable token is emitted at every level, a depth D document costs O(D²) rather than O(D) to process. The issue is triggered by nesting depth rather than byte volume, including the documented pick({filter: 'data'}) traversal-until-match path, so an application that sends untrusted JSON through a string or RegExp filter can block the Node.js event loop and cause denial of service with a small deeply nested document. The streamArray, streamObject, and streamValues streamers are not affected because they use the constant-time asm.depth getter. This issue is fixed in version 3.5.0.

• CWE-407Inefficient Algorithmic ComplexityAn algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.