CVE-2026-90583Network attack vector

Reflected XSS via unescaped raw query string

Published Sep 13, 2026 · Updated Sep 13, 2026

Reflected XSS in Kagi Small Web allows remote attackers to execute script in a browser through a crafted qs query string. The index function in app/sw.py renders Werkzeug's raw request.query_string as qs without neutralizing unencoded double quotes, allowing them to escape the HTML context. Delivery requires a raw HTTP request because ordinary browsers encode double quotes as %22; the effect is confined to script execution in the reflected response context.

CVSS severityUnavailable
Unscored
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Reflected XSS in Kagi Small Web allows remote attackers to execute script in a browser through a crafted qs query string. The index function in app/sw.py renders Werkzeug's raw request.query_string as qs without neutralizing unencoded double quotes, allowing them to escape the HTML context. Delivery requires a raw HTTP request because ordinary browsers encode double quotes as %22; the effect is confined to script execution in the reflected response context.

The record

CVE
CVE-2026-90583
Published
Sep 13, 2026
Updated
Sep 13, 2026
Vendor
Kagi
Product
Kagi Small Web
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 13, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=0ecb9c48edbf98dc7e934b54fbac43869e64b4cf

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Kagi · Kagi Small Webversion=0ecb9c48edbf98dc7e934b54fbac43869e64b4cf

Published CVSS scores

No CVSS assessment is available in this record.

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo