XSS in Vercel Next.js
CVE-2026-44581
Next.js is a React framework for building full-stack web applications. From 13.4.0 to before 15.5.16 and 16.2.5, App Router applications that rely on CSP nonces can be vulnerable to stored cross-site scripting when deployed behind shared caches. In affected versions, malformed nonce values derived from request headers could be reflected into rendered HTML in an unsafe way, allowing an attacker to poison cached responses and cause script execution for later visitors. This vulnerability is fixed in 15.5.16 and 16.2.5.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.7 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.002 (14.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 14th percentile — 14.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000
Affected products
- Vercel Next.js — versions >= 13.4.0, < 15.5.16, >= 16.0.0, < 16.2.5
Weakness classification (CWE)
References
- github.com/vercel/next.js/security/advisories/GHSA-ffhc-5mcf-pf4q (Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-44581?
- CVE-2026-44581 is a medium-severity vulnerability in Vercel Next.js, classified under Cross-site Scripting. CVSS score: 4.7/10. Published 2026-05-13.
- How severe is CVE-2026-44581?
- Medium severity. CVSS v3 base score is 4.7 out of 10.