CVE-2021-33500 Denial of service in n/a

High 7.5 Published 21 May 2021 Updated 3 Aug 2024

A remote server can cause a denial of service in PuTTY by rapidly changing the window title, leading to a GUI hang.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2021-33500?

CVE-2021-33500 is a high-severity denial of service vulnerability in n/a, published on 21 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

PuTTY before 0.75 on Windows allows remote servers to cause a denial of service (Windows GUI hang) by telling the PuTTY window to change its title repeatedly at high speed, which results in many SetWindowTextA or SetWindowTextW calls. NOTE: the same attack methodology may affect some OS-level GUIs on Linux or other platforms for similar reasons.

Which versions are affected by CVE-2021-33500?

It affects 1 product.

Products include Putty Putty.

How do I fix CVE-2021-33500?

No fix has been published for CVE-2021-33500 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-33500 being exploited?

There is no known exploitation of CVE-2021-33500 in the wild and no public exploit code.

Sources

Also known as CVE-2021-26940, GHSA-vmq2-m9cv-qwqx, UBUNTU-CVE-2021-33500.