Vulnerability Details : 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 category: Memory Corruption

Published 2021-07-22 17:15:09

Updated 2023-05-19 16:51:04

Source MITRE

View at NVD, CVE.org

Exploit prediction scoring system (EPSS) score for CVE-2021-29657

Probability of exploitation activity in the next 30 days: 0.28%

Percentile, the proportion of vulnerabilities that are scored at or less: ~ 64 % EPSS Score History EPSS FAQ

CVSS scores for CVE-2021-29657

Base Score	Base Severity	CVSS Vector	Exploitability Score	Impact Score	Source
6.9	MEDIUM	AV:L/AC:M/Au:N/C:C/I:C/A:C	3.4	10.0	[email protected]
Access Vector: Local Access Complexity: Medium Authentication: None Confidentiality Impact: Complete Integrity Impact: Complete Availability Impact: Complete
7.4	HIGH	CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H	1.4	5.9	[email protected]
Attack Vector: Local Attack Complexity: High Privileges Required: None User Interaction: None Scope: Unchanged Confidentiality: High Integrity: High Availability: High

CWE ids for CVE-2021-29657

CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state.

Assigned by: [email protected] (Primary)
CWE-416 Use After Free

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Assigned by: [email protected] (Primary)

References for CVE-2021-29657

https://bugs.chromium.org/p/project-zero/issues/detail?id=2177

Exploit;Mailing List;Patch;Third Party Advisory
https://security.netapp.com/advisory/ntap-20210902-0008/

Third Party Advisory
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.12

Exploit;Patch;Vendor Advisory
http://packetstormsecurity.com/files/163324/KVM-nested_svm_vmrun-Double-Fetch.html

Third Party Advisory;VDB Entry
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a58d9166a756a0f4a6618e4f593232593d6df134

Patch;Third Party Advisory

Products affected by CVE-2021-29657

Linux » Linux Kernel
Versions from including (>=) 5.11 and before (<) 5.11.12
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Matching versions
Linux » Linux Kernel
Versions from including (>=) 5.10 and before (<) 5.10.28
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Matching versions