CVE-2026-9520Public exploitNetwork attack vector

Script execution via unvalidated sign-in redirect

Published May 26, 2026 · Updated May 26, 2026

Cross-site scripting in Blitz 3.0.0 through 3.0.2 allows remote attackers to execute script through a crafted Next argument. The generated sign-in LoginForm passes the URL-derived Next value to client-side navigation without restricting executable schemes. A victim must open the crafted sign-in URL and complete authentication; the script then runs in that victim's browser context.

CVSS severity4.3
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Blitz 3.0.0 through 3.0.2 allows remote attackers to execute script through a crafted Next argument. The generated sign-in LoginForm passes the URL-derived Next value to client-side navigation without restricting executable schemes. A victim must open the crafted sign-in URL and complete authentication; the script then runs in that victim's browser context.

The record

CVE
CVE-2026-9520
Published
May 26, 2026
Updated
May 26, 2026
Vendor
Blitz.js
Product
Blitz
Classifications
CWE-79, CWE-94, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 26, 2026CVE publishedPublication date reported by the CVE source.
  2. May 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.0.0
  2. Affected versionversion=3.0.1
  3. Affected versionversion=3.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Blitz.js · Blitzversion=3.0.0; version=3.0.1; version=3.0.2

Published CVSS scores

5.0NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
4.3NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
2.1GitHubCVSS: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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-94Improper Control of Generation of Code ('Code Injection')
T1204.001Malicious Link

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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