CVE-2021-34556 Information disclosure in n/a

What is CVE-2021-34556?

CVE-2021-34556 is a medium-severity vulnerability in Debian Debian Linux, published on 2 Aug 2021. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel through 5.13.7, an unprivileged BPF program can obtain sensitive information from kernel memory via a Speculative Store Bypass side-channel attack because the protection mechanism neglects the possibility of uninitialized memory locations on the BPF stack.

Weakness: CWE-203

Which versions are affected by CVE-2021-34556?

It affects 3 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Linux kernel.

How do I fix CVE-2021-34556?

Apply the vendor's patch.

Is CVE-2021-34556 being exploited?

There is no known exploitation of CVE-2021-34556 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-196011539, AZL-6566, DEBIAN-CVE-2021-34556, GHSA-r297-r893-jqqx, PUB-A-196011539, UBUNTU-CVE-2021-34556.