On March 31, the Linux kernel privilege escalation vulnerability demonstrated by the competitor Manfred Paul on the Pwn2Own contest was included in the CVE database and identified as CVE-2020-8835. This vulnerability exists because the bpf verifier in the Linux kernel does not properly calculate register bounds for certain operations. A local attacker could exploit this vulnerability to read confidential information (kernel memory) or gain administrative privileges. Users should take preventive measures as soon as possible.
Scope of Impact
- Linux Kernel 5.4
- Linux Kernel 5.5
- Version Check
Users of the Linux system could run the following command to check the current version to determine whether it is vulnerable:
Affected users could upgrade the Linux kernel for protection by downloading updates from the following link:
For the vulnerable and fixed Debian Bullseye releases, visit the following link:
For details on Ubuntu distributions, visit the following link:
If users cannot update the Linux kernel for the time being, they can adopt the mitigation measure, that is, modifying a kernel parameter to restrict access from ordinary users.
Set kernel.unprivileged_bpf_disabled sysctl to 1.
$ sudo sysctl kernel.unprivileged_bpf_disabled=1
This issue can be mitigated on a system using a secure boot.
# sysctl -w kernel.unprivileged_bpf_disabled=1
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