CVE-2023-1998

MEDIUM

Published 2023-04-21T14:51:52.907Z

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CVSS Score

V3.1

5.6

/10

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

Base Score Metrics

Exploitability: N/A Impact: N/A

EPSS Score

v2023.03.01

0.001

probability

of exploitation in the wild

There is a 0.1% chance that this vulnerability will be exploited in the wild within the next 30 days.

Updated: 2025-01-25

Exploit Probability

Percentile: 0.417

Higher than 41.7% of all CVEs

Attack Vector Metrics

Attack Vector

LOCAL

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

NONE

Scope

CHANGED

Impact Metrics

Confidentiality

HIGH

Integrity

NONE

Availability

NONE

Description

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.