Use After Free in Linux Kernel
CVE-2021-29657
arch/x86/kvm/svm/nested.c in the Linux kernel before 5.11.12 has a use-after-free in which an AMD KVM guest can bypass access control on host OS MSRs when there are nested guests, aka CID-a58d9166a756. This occurs because of a TOCTOU race condition associated with a VMCB12 double fetch in nested_svm_vmrun.
Vulnerability class: TOCTOU (Time-of-Check to Time-of-Use)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.004 (33.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 34th percentile — 33.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
- ARPSyndicate/cve-scores
- ARPSyndicate/cvemon
- kdn111/linux-kernel-exploitation
- khanhdn111/linux-kernel-exploitation
- khanhdz-06/linux-kernel-exploitation
- khanhdz191/linux-kernel-exploitation
- khanhhdz/linux-kernel-exploitation
- khanhhdz06/linux-kernel-exploitation
- khanhnd123/linux-kernel-exploitation
- khnhdz/linux-kernel-exploitation
References
- packetstormsecurity.com/files/163324/KVM-nested_svm_vmrun-Double-Fetch.html (VDB Entry, Third Party Advisory)
- bugs.chromium.org/p/project-zero/issues/detail (Exploit, Patch, Mailing List, Third Party Advisory)
- git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/ (Patch, Third Party Advisory)
- cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.12 (Exploit, Patch, Vendor Advisory)
- security.netapp.com/advisory/ntap-20210902-0008/ (Third Party Advisory)
Frequently asked questions
- What is CVE-2021-29657?
- CVE-2021-29657 is a high-severity vulnerability in Linux Kernel, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 7.4/10. Published 2021-07-22.
- How severe is CVE-2021-29657?
- High severity. CVSS v3 base score is 7.4 out of 10.
- Is CVE-2021-29657 known to be exploited?
- 16 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.