# CVE-2026-100081: Linux kernel xen-netback use-after-free in mcast_addr_list_free

Source: https://junglewise.ai/threats/cve-2026-100081-in-the-linux-kernel-the-following-vulnerability-has-been  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-06. Updated: 2026-11-06  
License: CC BY 4.0 with a link back

CVE-2026-100081 · Severity: info · Published 2026-11-06

A race condition exists in the Linux kernel's Xen network backend driver where a multicast address list is freed while still being accessed by transmission and reception processing threads. An attacker with access to the hypervisor or guest domain could trigger a use-after-free condition, leading to kernel memory corruption and potential privilege escalation.

Technologies: [Linux kernel](https://junglewise.ai/threats/technologies/x-linux-kernel).

## Quick answers

**Is CVE-2026-100081 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-100081 being exploited in the wild.

**How severe is CVE-2026-100081?** Informational severity, published 6 November 2026.

**Which products and versions are affected?** Linux kernel All versions prior to fix.

**Is there a fix for CVE-2026-100081?** A patch was published on 2026-11-06. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-100081 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-100081?** Check whether you run Linux kernel at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A use-after-free vulnerability in xen-netback's xenvif_mcast_addr_list_free() function arises because the cleanup was called before TX/RX processing had fully stopped. The lookups from xenvif_start_xmit() and adds/removes from xenvif_tx_action() could access freed memory. The fix defers the cleanup call to backend_disconnect() past the synchronize_net() synchronization point, ensuring all active processing has ceased before memory is freed.

## Affected products

- Linux kernel All versions prior to fix

## Timeline

- 2026-11-06: disclosed
- 2026-11-06: patched

## References

- [https://git.kernel.org/stable/c/0d515c409033c8e2a645a781be3ca76ab825fc8c](https://git.kernel.org/stable/c/0d515c409033c8e2a645a781be3ca76ab825fc8c)
- [https://git.kernel.org/stable/c/0e786123e46d08d2247ce93a5435e45ed9f4c5d1](https://git.kernel.org/stable/c/0e786123e46d08d2247ce93a5435e45ed9f4c5d1)

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