Improper input validation in Zen-Browser Desktop

CVE-2026-44658

Zen is a firefox-based browser. Prior to 1.19.12b, RSS feed URLs entered by the user are validated to http: or https: in promptForFeedUrl, but item links inside the feed are not subject to the same restriction. The provider maps each RSS/Atom item link into item.url, filters only for presence and date, and returns the item list. The live-folder manager later creates pinned lazy tabs from these values with gBrowser.addTrustedTab(item.url, ...). This vulnerability is fixed in 1.19.12b.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 2.4 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (16.9th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 17th percentile — 16.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-44658: held from 0.002 to 0.003.

EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-44658?
CVE-2026-44658 is a low-severity vulnerability in Zen-Browser Desktop, classified under Improper Input Validation. CVSS score: 2.4/10. Published 2026-05-11.
How severe is CVE-2026-44658?
Low severity. CVSS v3 base score is 2.4 out of 10.