$ cve CVE-2023-1998 JSON

CVE-2023-1998 EXPLOIT

5.6

MEDIUM · CVSS 3.1 · EPSS 1.4% (pctl 71)

Patch early

A public exploit exists.

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.

Scoring

CVSS	5.6 (MEDIUM, v3.1)
Vector	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
EPSS	1.38% — more likely to be exploited than 71% of all CVEs
Weakness	CWE-1303
On CISA KEV	no
Public exploit	yes
Published	2023-04-21
Last modified	2026-06-17

Affected (2)

Vendor	Product
debian	debian linux
linux	linux kernel

Public exploits

Source	Title	Date
exploit-db	Linux Kernel 6.2 - Userspace Processes To Enable Mitigation	2023-04-20

References

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