Vulnerability in IBM Power8
CVE-2020-8834
KVM in the Linux kernel on Power8 processors has a conflicting use of HSTATE_HOST_R1 to store r1 state in kvmppc_hv_entry plus in kvmppc_{save,restore}_tm, leading to a stack corruption. Because of this, an attacker with the ability run code in kernel space of a guest VM can cause the host kernel to panic. There were two commits that, according to the reporter, introduced the vulnerability: f024ee098476 ("KVM: PPC: Book3S HV: Pull out TM state save/restore into separate procedures") 87a11bb6a7f7 ("KVM: PPC: Book3S HV: Work around XER[SO] bug in fake suspend mode") The former landed in 4.8, the latter in 4.17. This was fixed without realizing the impact in 4.18 with the following three commits, though it's believed the first is the only strictly necessary commit: 6f597c6b63b6 ("KVM: PPC: Book3S PR: Add guest MSR parameter for kvmppc_save_tm()/kvmppc_restore_tm()") 7b0e827c6970 ("KVM: PPC: Book3S HV: Factor fake-suspend handling out of kvmppc_save/restore_tm") 009c872a8bc4 ("KVM: PPC: Book3S PR: Move kvmppc_save_tm/kvmppc_restore_tm to separate file")
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.003 (25.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 25.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- IBM Power8
- Linux Kernel
- Linux Kernel — versions 4.8, unspecified
- Canonical Ubuntu Linux — versions 16.04, 18.04
- openSUSE Leap — versions 15.1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- www.openwall.com/lists/oss-security/2020/04/06/2 (Mailing List, Third Party Advisory)
- usn.ubuntu.com/usn/usn-4318-1 (Third Party Advisory)
- bugs.launchpad.net/ubuntu/+source/linux/+bug/1867717 (Exploit, Third Party Advisory)
- usn.ubuntu.com/4318-1/ (vendor-advisory, Third Party Advisory)
- lists.opensuse.org/opensuse-security-announce/2020-04/msg00035.html (vendor-advisory, Mailing List, Third Party Advisory)
Frequently asked questions
- What is CVE-2020-8834?
- CVE-2020-8834 is a medium-severity vulnerability in IBM Power8, classified under CWE-368. CVSS score: 6.5/10. Published 2020-04-09.
- How severe is CVE-2020-8834?
- Medium severity. CVSS v3 base score is 6.5 out of 10.
- Is CVE-2020-8834 known to be exploited?
- 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.