# CVE-2026-80866: tipc: avoid busy looping in tipc_exit_net()

CVE-2026-80866 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-80866, released September 5, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-80866
- Priority: Routine
- CVSS: 4.1 (Moderate)
- EPSS: 0.0020
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 4, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-80866

## Description

In the Linux kernel, the following vulnerability has been resolved:  tipc: avoid busy looping in tipc_exit_net()  Blamed commit introduced a busy-wait loop in tipc_exit_net() to wait for pending UDP bearer cleanup works to complete:         while (atomic_read(&tn->wq_count))                cond_resched();  This loop can busy-wait for a long time if cond_resched() is a NOP. This typically happens if the netns exit is executed by a high priority task, or under kernels configured without preemption (CONFIG_PREEMPT_NONE). In such cases, it wastes CPU cycles and can lead to soft lockups.  Fix this by replacing the busy loop with wait_var_event(), allowing the thread to sleep properly until the work queue count reaches zero.  Accordingly, update cleanup_bearer() to use atomic_dec_and_test() and wake_up_var() to wake up the waiter when the count drops to zero.  This uses the global wait queue hash table, avoiding the need to bloat struct tipc_net with a wait_queue_head_t. The atomic_dec_and_test() provides the necessary memory barrier to ensure the wakeup is not missed.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.115-2 | [DEBIAN-CVE-2026-80866](https://patchblox.com/security/data/fix/linux/debian-cve-2026-80866.md) | Sep 5, 2026 |
| Linux | linux Debian 14 | 7.1.5-1 | [DEBIAN-CVE-2026-80866](https://patchblox.com/security/data/fix/linux/debian-cve-2026-80866.md) | Sep 5, 2026 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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