CVE-2021-34556

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.

CVSS 3.1

5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

EPSS

0.4% chance of exploitation in the next 30 days; higher than 35% of CVEs (scores of 2026-10-25)

CWE

CWE-203

Published

2021-08-02

Modified

2026-10-08

Record from

the NVD, synced 2026-10-19

Affected

• debian:debian_linux
• fedoraproject:fedora
• linux:linux_kernel

References

• http://www.openwall.com/lists/oss-security/2021/08/01/3
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/?id=2039f26f3aca5b0e419b98f65dd36481337b86ee
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/?id=f5e81d1117501546b7be050c5fbafa6efd2c722c
• https://lists.debian.org/debian-lts-announce/2021/10/msg00010.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/565ZS55ZFEN62WVRRORT7R63RXW5F4T4/

Check your stackJSON