CVE-2020-25656 Use after free in kernel

What is CVE-2020-25656?

CVE-2020-25656 is a medium-severity use after free vulnerability in Debian Debian Linux, published on 2 Dec 2020. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

A flaw was found in the Linux kernel. A use-after-free was found in the way the console subsystem was using ioctls KDGKBSENT and KDSKBSENT. A local user could use this flaw to get read memory access out of bounds. The highest threat from this vulnerability is to data confidentiality.

Weakness: CWE-416

Which versions are affected by CVE-2020-25656?

It affects 4 products.

Products include Debian Debian Linux, Linux kernel, Redhat Enterprise Linux, Starwindsoftware Starwind Virtual San.

How do I fix CVE-2020-25656?

Apply the vendor's patch.

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-2020-25656 being exploited?

There is no known exploitation of CVE-2020-25656 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as A-174904705, DEBIAN-CVE-2020-25656, GHSA-4pfp-w4vm-364q, PUB-A-174904705, UBUNTU-CVE-2020-25656.