CVE-2026-48850 Use after free in PuTTY

Low 3.7 Published 25 May 2026 Updated 26 May 2026

A double free vulnerability in PuTTY's RSA key exchange allows attackers to potentially execute arbitrary code or cause a denial of service.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-48850?

CVE-2026-48850 is a low-severity use after free vulnerability in PuTTY, published on 25 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

PuTTY 0.72 before 0.84 has a double free in RSA KEX.

Weakness: CWE-415

Which versions are affected by CVE-2026-48850?

It affects 1 product.

Products include Putty Putty.

How do I fix CVE-2026-48850?

Upgrade to a fixed version.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-48850 being exploited?

There is no known exploitation of CVE-2026-48850 in the wild and no public exploit code.

Sources

Also known as DEBIAN-CVE-2026-48850, GHSA-c27j-mcjp-93gg, UBUNTU-CVE-2026-48850.