RCE in Blitz-Js Blitz
CVE-2026-9520
A weakness has been identified in blitz-js blitz up to 3.0.2 on GitHub. This impacts an unknown function of the file packages/generator/templates/app/src/app/auth/components/LoginForm.tsx of the component Sign-in. This manipulation of the argument Next causes cross site scripting. It is possible to initiate the attack remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (36.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 36.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001
Affected products
- Blitz-Js Blitz — versions 3.0.0, 3.0.1, 3.0.2
Weakness classification (CWE)
References
- vuldb.com/vuln/365540 (technical-description, vdb-entry)
- vuldb.com/vuln/365540/cti (signature, permissions-required)
- vuldb.com/submit/814378 (third-party-advisory)
- gist.github.com/TrebledJ/164c7ca6c8208b63e6937bc11984720b (exploit)
Frequently asked questions
- What is CVE-2026-9520?
- CVE-2026-9520 is a medium-severity vulnerability in Blitz-Js Blitz, classified under Cross-site Scripting. CVSS score: 4.3/10. Published 2026-05-26.
- How severe is CVE-2026-9520?
- Medium severity. CVSS v3 base score is 4.3 out of 10.