CVE-2020-27170

Published: 18 March 2021

An issue was discovered in the Linux kernel before 5.11.8. kernel/bpf/verifier.c performs undesirable out-of-bounds speculation on pointer arithmetic, leading to side-channel attacks that defeat Spectre mitigations and obtain sensitive information from kernel memory, aka CID-f232326f6966. This affects pointer types that do not define a ptr_limit.

From the Ubuntu security team

Piotr Krysiuk discovered that the BPF subsystem in the Linux kernel did not properly apply speculative execution limits on some pointer types. A local attacker could use this to expose sensitive information (kernel memory).

Priority

High

CVSS 3 base score: 4.7

Status

Notes

According to the upstream advisory,
f232326f6966cf2a1d1db7bc917a4ce5f9f55f76 is the minimal fix but the whole
series should be applied together

kernels before 4.15 are not affected by this.

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-27170
• https://www.openwall.com/lists/oss-security/2021/03/19/2
• https://usn.ubuntu.com/usn/usn-4887-1
• https://usn.ubuntu.com/usn/usn-4890-1
• NVD
• Launchpad
• Debian