What is CVE-2026-90583?

CVE-2026-90583 is a medium-severity vulnerability in Kagisearch Smallweb, classified under Cross-site Scripting. CVSS score: 4.3/10. Published 2026-09-13.

How severe is CVE-2026-90583?

Medium severity. CVSS v3 base score is 4.3 out of 10.

RCE in Kagisearch Smallweb

CVE-2026-90583

A security flaw has been discovered in kagisearch smallweb up to 0ecb9c48edbf98dc7e934b54fbac43869e64b4cf. The affected element is the function index of the file app/sw.py of the component Query String Rendering. Performing a manipulation of the argument qs results in cross site scripting. The attack is possible to be carried out remotely. This product adopts a rolling release strategy to maintain continuous delivery. Therefore, version details for affected or updated releases cannot be specified. The patch is named 00b68144e583f20a6b67e29cf01bc07f57979ffb. It is recommended to apply a patch to fix this issue. Exploitability requires a raw HTTP request carrying unencoded double-quote characters in the query string - Werkzeug's request.query_string returns the raw request-target, and ordinary browsers percent-encode " as %22, so the payload only lands via netcat/curl-style raw sockets.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-09-13 · last modified 2026-09-15.

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: 0.005 (41.8th percentile), scored 2026-10-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 42nd percentile — 41.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Kagisearch Smallweb — versions 0ecb9c48edbf98dc7e934b54fbac43869e64b4cf

Weakness classification (CWE)

References

vuldb.com/vuln/403168 (technical-description, vdb-entry)
vuldb.com/vuln/403168/cti (signature, permissions-required)
vuldb.com/cve/CVE-2026-90583 (third-party-advisory)
vuldb.com/submit/913779 (third-party-advisory)
github.com/kagisearch/smallweb/issues/854 (issue-tracking)
github.com/kagisearch/smallweb/commit/00b68144e583f20a6b67e29cf01bc07f57979ffb (patch)
github.com/kagisearch/smallweb/ (product)

Frequently asked questions

What is CVE-2026-90583?: CVE-2026-90583 is a medium-severity vulnerability in Kagisearch Smallweb, classified under Cross-site Scripting. CVSS score: 4.3/10. Published 2026-09-13.
How severe is CVE-2026-90583?: Medium severity. CVSS v3 base score is 4.3 out of 10.