CVE-2021-39923 Denial of service in Wireshark

What is CVE-2021-39923?

CVE-2021-39923 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 19 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Large loop in the PNRP dissector in Wireshark 3.4.0 to 3.4.9 and 3.2.0 to 3.2.17 allows denial of service via packet injection or crafted capture file

Weakness: CWE-834

Which versions are affected by CVE-2021-39923?

It affects 2 products.

Products include Debian Debian Linux, Wireshark Wireshark.

How do I fix CVE-2021-39923?

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-2021-39923 being exploited?

There is no known exploitation of CVE-2021-39923 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 AZL-7411, DEBIAN-CVE-2021-39923, GHSA-v75m-35ph-56m2, UBUNTU-CVE-2021-39923.