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
Products affected by CVE-2021-29657
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Exploit prediction scoring system (EPSS) score for CVE-2021-29657
0.28%
Probability of exploitation activity in the next 30 days
EPSS Score History
~ 68 %
Percentile, the proportion of vulnerabilities that are scored at or less
CVSS scores for CVE-2021-29657
| Base Score | Base Severity | CVSS Vector | Exploitability Score | Impact Score | Score Source | First Seen |
|---|---|---|---|---|---|---|
|
6.9
|
MEDIUM | AV:L/AC:M/Au:N/C:C/I:C/A:C |
3.4
|
10.0
|
NIST | |
|
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
|
NIST |
CWE ids for CVE-2021-29657
-
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: nvd@nist.gov (Primary)
-
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.Assigned by: nvd@nist.gov (Primary)
References for CVE-2021-29657
-
https://bugs.chromium.org/p/project-zero/issues/detail?id=2177
2177 - KVM: double fetch in nested_svm_vmrun can lead to unrestricted MSR access - project-zeroExploit;Mailing List;Patch;Third Party Advisory
-
https://security.netapp.com/advisory/ntap-20210902-0008/
CVE-2021-29657 Linux Kernel Vulnerability in NetApp Products | NetApp Product SecurityThird Party Advisory
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https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.12
Exploit;Patch;Vendor Advisory
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http://packetstormsecurity.com/files/163324/KVM-nested_svm_vmrun-Double-Fetch.html
KVM nested_svm_vmrun Double Fetch ≈ Packet StormThird Party Advisory;VDB Entry
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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a58d9166a756a0f4a6618e4f593232593d6df134
kernel/git/torvalds/linux.git - Linux kernel source treePatch;Third Party Advisory
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