CVE-2026-100409: opennextjs opennextjs-cloudflare

Vulnerability summary

CVE-2026-100409 is a high (CVSS 7.5) vulnerability in opennextjs opennextjs-cloudflare. EPSS estimates a 0.30% chance of exploitation in the next 30 days, higher than 22% of scored vulnerabilities.

Timeline

1. 15-10-2026
   PublishedVulnerability first disclosed.
2. 15-10-2026
   Last modifiedVulnerability information updated.

Description

OpenNext Cloudflare is an open Next.js adapter for Cloudflare. From 0.3.0 until 1.20.2, applications that enable enableCacheInterception, rely on middleware for access control, and have a matching cached protected route process encoded pathnames inconsistently between middleware matching and cache lookup. An unauthenticated attacker can use a percent-encoded pathname that does not match authorization middleware but decodes to the cache key of a protected route, causing cached content to be returned without authorization. Malformed encodings can also be partially decoded, allowing cache lookup to continue with a pathname that middleware did not evaluate consistently. This issue is fixed in version 1.20.2.

• CWE-177Improper Handling of URL Encoding (Hex Encoding)The product does not properly handle when all or part of an input has been URL encoded.
• CWE-180Incorrect Behavior Order: Validate Before CanonicalizeThe product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step.