CVE-2023-1998

high

Published 2023-08-01 · Modified 2023-11-14

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CVSS v3

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CVSS v4 NEW

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not yet in upstream

VIR risk

9.0

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.

Predictions

Exploit likelihood

55%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

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Exploits

Public proof-of-concept code below. AS-IS, for defenders and authorised testing only.

Exploit-DB

EDB-51384 local linux

nu11secur1ty · 2023-04-20

Linux Kernel 6.2 - Userspace Processes To Enable Mitigation

Source code queued for fetch — refresh in a moment.

OS impact

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

AlmaLinux Fixed 2 releases

Version	Status	Fixed in
9	Fixed	`kernel-64k-devel-matched-5.14.0-284.25.1.el9_2.aarch64.rpm`
8	Fixed	`kernel-doc-4.18.0-513.5.1.el8_9.noarch.rpm`

Debian Fixed 5 releases

Version	Status	Fixed in
trixie	Fixed	`6.1.20-1`
sid	Fixed	`6.1.20-1`
forky	Fixed	`6.1.20-1`
bullseye	Fixed	`5.10.178-1`
bookworm	Fixed	`6.1.20-1`

Red Hat Fixed 2 releases

Version	Status	Fixed in
9	Fixed	—
8	Fixed	—

Rocky Linux Fixed 1 release

Version	Status	Fixed in
9	Fixed	—

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.