CVE-2026-89020 MikroTik RouterOS Stack Buffer Overflow via TFTP URL Path
Authenticated users can crash the mtget worker process via a stack buffer overflow in the TFTP URL path handler, causing denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-89020?
CVE-2026-89020 is a medium-severity memory corruption vulnerability in MikroTik RouterOS, published on 14 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
MikroTik RouterOS before 7.23.4 (long-term) and 7.24.2 (stable) contains a stack-based buffer overflow vulnerability in the mtget binary's TFTP RRQ builder function that allows authenticated users to crash the mtget worker process by supplying a URL path of 507 bytes or more to the /tool fetch command; the first write outside the 528-byte buffer occurs at 505 bytes. Attackers can trigger the overflow by issuing a fetch command with a crafted tftp:// URL path, which causes an unbounded rep movsb instruction to overwrite saved registers at a deterministic offset, crashing the process without requiring a reachable TFTP server or elevated privileges beyond read-only group membership.
Weakness: CWE-121
Which versions are affected by CVE-2026-89020?
How do I fix CVE-2026-89020?
No fix has been published for CVE-2026-89020 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-2026-89020 being exploited?
There is no known exploitation of CVE-2026-89020 in the wild and no public exploit code.
Sources
Also known as GHSA-66qh-8rrp-pqjv.