CVE-2026-118664: decode-uri-component: Denial of service via quadratic replacement of percent-encoded runs

Vulnerability summary

CVE-2026-118664 is a high (CVSS 8.2) Uncontrolled Resource Consumption vulnerability in samverschueren decode-uri-component. EPSS estimates a 0.32% chance of exploitation in the next 30 days, higher than 24.8% of scored vulnerabilities.

Timeline

1. 28-10-2026
   PublishedVulnerability first disclosed.
2. 29-10-2026
   Last modifiedVulnerability information updated.

Description

decode-uri-component provides a more robust alternative to decodeURIComponent. Prior to 0.5.1, decodeUriComponent in index.js falls back to customDecodeURIComponent after native decoding throws, and the fallback collects every distinct percent-encoded run before performing a full-string regular-expression replacement for each entry. Malformed input containing many distinct runs can therefore make both the number of replacements and the scanned input length grow together, causing quadratic CPU consumption and blocking the Node.js event loop; request-body inputs can reach the demonstrated size, while ordinary URL header limits reduce the practical delay. This issue is fixed in version 0.5.1.

• CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
• 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.