blitz-js blitz Sign-in LoginForm.tsx cross site scripting

published 2026-05-26 5 mo ago modified 2026-07-23 3 mo ago also GHSA-h2p9-cr4h-px24 , EUVD-2026-31781

cvss: 4.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits: 0; none known

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.

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-9520 updated 2026-06-28 cvss 5.4

blitz: blitz-js blitz: Cross-site scripting via 'Next' argument manipulation

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 5 mo ago (2026-05-27)

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

gist.github.com https://gist.github.com/TrebledJ/164c7ca6c8208b63e6937bc11984720b referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	5.3	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
CNA	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N/E:P/RL:X/RC:R
CNA	3.0	4.3	CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N/E:P/RL:X/RC:R
CNA	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N/E:POC/RL:ND/RC:UR
CNA	4.0	2.1	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CNA	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
CNA	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N
GitHub	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	blitz	<=3.0.2	no fix listed

Affected products

blitz-js blitz

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation
CWE-94 Improper Control of Generation of Code

References

gist.github.com /TrebledJ/164c7ca6c8208b63e6937bc11984720b
exploit, web
vuldb.com /vuln/365540
vdb-entry, technical-description, web
vuldb.com /vuln/365540/cti
signature, permissions-required, web
vuldb.com /submit/814378
third-party-advisory, web
nvd.nist.gov /vuln/detail/CVE-2026-9520
advisory
github.com /blitz-js/blitz
package

Sources

CVE List CVE-2026-9520
GitHub Advisory GHSA-h2p9-cr4h-px24
NVD CVE-2026-9520

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary