CVE-2026-100409 (CVSS 7.5)

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.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Weakness Type (CWE)

CWE-177 CWE-177

CWE-180 CWE-180

References

Other References

https://github.com/opennextjs/opennextjs-aws/pull/1199 https://github.com/opennextjs/opennextjs-aws/pull/1200 https://github.com/opennextjs/opennextjs-cloudflare/commit/38ea40b669be272ddf09a7df7e70c69d0b57404b https://github.com/opennextjs/opennextjs-cloudflare/releases/tag/@opennextjs/[email protected] https://github.com/opennextjs/opennextjs-cloudflare/security/advisories/GHSA-2vc4-c4r6-p6v6

Frequently Asked Questions

What is CVE-2026-100409? +

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-100409? +

CVE-2026-100409 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

How do I check if I'm vulnerable to CVE-2026-100409? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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