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cve[email protected]CVE-2023-1998
HistoryApr 21, 2023 - 3:15 p.m.

CVE-2023-1998

2023-04-2115:15:07
CWE-203
CWE-1303
web.nvd.nist.gov
148
linux kernel
userspace processes
mitigations
prctl
seccomp
spectre-bti
vms
cloud provider
ibrs
stibp
branch target injection

5.6 Medium

CVSS3

Attack Vector

LOCAL

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

6.2 Medium

AI Score

Confidence

High

1 Low

CVSS2

Access Vector

LOCAL

Access Complexity

HIGH

Authentication

SINGLE

Confidentiality Impact

PARTIAL

Integrity Impact

NONE

Availability Impact

NONE

AV:L/AC:H/Au:S/C:P/I:N/A:N

0.0004 Low

EPSS

Percentile

12.9%

The Linux kernel allows userspace processes to enable mitigations by calling prctl with PR_SET_SPECULATION_CTRL which disables the speculation feature as well as by using seccomp. We had noticed that on VMs of at least one major cloud provider, the kernel still left the victim process exposed to attacks in some cases even after enabling the spectre-BTI mitigation with prctl. The same behavior can be observed on a bare-metal machine when forcing the mitigation to IBRS on boot command line.

This happened because when plain IBRS was enabled (not enhanced IBRS), the kernel had some logic that determined that STIBP was not needed. The IBRS bit implicitly protects against cross-thread branch target injection. However, with legacy IBRS, the IBRS bit was cleared on returning to userspace, due to performance reasons, which disabled the implicit STIBP and left userspace threads vulnerable to cross-thread branch target injection against which STIBP protects.

5.6 Medium

CVSS3

Attack Vector

LOCAL

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

6.2 Medium

AI Score

Confidence

High

1 Low

CVSS2

Access Vector

LOCAL

Access Complexity

HIGH

Authentication

SINGLE

Confidentiality Impact

PARTIAL

Integrity Impact

NONE

Availability Impact

NONE

AV:L/AC:H/Au:S/C:P/I:N/A:N

0.0004 Low

EPSS

Percentile

12.9%