CVE-2021-40516 Denial of service in n/a

What is CVE-2021-40516?

CVE-2021-40516 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 5 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

WeeChat before 3.2.1 allows remote attackers to cause a denial of service (crash) via a crafted WebSocket frame that trigger an out-of-bounds read in plugins/relay/relay-websocket.c in the Relay plugin.

Weakness: CWE-125

Which versions are affected by CVE-2021-40516?

It affects 2 products.

Products include Debian Debian Linux, Weechat Weechat.

How do I fix CVE-2021-40516?

Upgrade to a fixed version.

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-2021-40516 being exploited?

There is no known exploitation of CVE-2021-40516 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 DEBIAN-CVE-2021-40516, GHSA-82mm-45xg-j4xh, MGASA-2021-0466, UBUNTU-CVE-2021-40516, openSUSE-SU-2022:0083-1.