CVE-2026-41431 Zen Browser MAR updater ships with signature verification removed — unsigned updates accepted
Attackers can deliver arbitrary unsigned code to all Zen Browser users via the auto-update mechanism if the update server is compromised.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-41431?
CVE-2026-41431 is a high-severity vulnerability in zen-browser desktop, published on 11 May 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
Zen is a firefox-based browser. Prior to 1.19.9b, Zen Browser ships a Mozilla Application Resource (MAR) updater (org.mozilla.updater) that has had all MAR signature verification stripped from the Firefox codebase it was forked from. The MAR files served to users contain zero cryptographic signatures, and the updater binary contains zero cryptographic verification code. This eliminates the defense-in-depth that MAR signing provides. If the update server or GitHub release pipeline is compromised, arbitrary unsigned code can be delivered to all Zen users via the auto-update mechanism. This vulnerability is fixed in 1.19.9b.
Weakness: CWE-347
Which versions are affected by CVE-2026-41431?
How do I fix CVE-2026-41431?
No fix has been published for CVE-2026-41431 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-41431 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-41431 exists.
Sources
Also known as GHSA-qpj9-m8jc-mw6q.