CVE-2026-3870 Memory corruption in VMG4005-B50B firmware
An adjacent attacker can trigger a temporary denial-of-service condition in the UPnP function of Zyxel VMG4005-B50B routers via a buffer overflow.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-3870?
CVE-2026-3870 is a medium-severity memory corruption vulnerability in Zyxel VMG4005-B50B firmware, published on 2 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
A buffer overflow vulnerability in the UPnP AddPortMapping() command in Zyxel VMG4005-B50B firmware versions through 5.13(ABRL.5.4)C0 could allow an adjacent attacker to trigger a temporary denial-of-service (DoS) condition affecting the UPnP function of the affected device.
Weakness: CWE-120
Which versions are affected by CVE-2026-3870?
How do I fix CVE-2026-3870?
No fix has been published for CVE-2026-3870 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-3870 being exploited?
There is no known exploitation of CVE-2026-3870 in the wild and no public exploit code.
Sources
Also known as GHSA-r75m-m2v9-89vv.