Vulnerability Details : CVE-2023-1998
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.
Exploit prediction scoring system (EPSS) score for CVE-2023-1998
Probability of exploitation activity in the next 30 days: 0.05%
Percentile, the proportion of vulnerabilities that are scored at or less: ~ 13 % EPSS Score History EPSS FAQ
CVSS scores for CVE-2023-1998
Base Score | Base Severity | CVSS Vector | Exploitability Score | Impact Score | Score Source |
---|---|---|---|---|---|
5.6
|
MEDIUM | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N |
1.1
|
4.0
|
Google Inc. |
5.6
|
MEDIUM | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N |
1.1
|
4.0
|
NIST |
CWE ids for CVE-2023-1998
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The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not.Assigned by: nvd@nist.gov (Primary)
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Hardware structures shared across execution contexts (e.g., caches and branch predictors) can violate the expected architecture isolation between contexts.Assigned by: cve-coordination@google.com (Secondary)
References for CVE-2023-1998
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https://lists.debian.org/debian-lts-announce/2023/05/msg00006.html
[SECURITY] [DLA 3403-1] linux security updateMailing List;Third Party Advisory
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https://github.com/google/security-research/security/advisories/GHSA-mj4w-6495-6crx
Linux Kernel: Spectre v2 SMT mitigations problem · Advisory · google/security-research · GitHubExploit;Third Party Advisory
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https://lists.debian.org/debian-lts-announce/2023/05/msg00005.html
[SECURITY] [DLA 3404-1] linux-5.10 security updateMailing List;Third Party Advisory
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https://github.com/torvalds/linux/commit/6921ed9049bc7457f66c1596c5b78aec0dae4a9d
x86/speculation: Allow enabling STIBP with legacy IBRS · torvalds/linux@6921ed9 · GitHubPatch
Products affected by CVE-2023-1998
- cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*