# CVE-2026-72389: bridge: stp: Fix a potential use-after-free when deleting a bridge

> A missing check in Linux kernel bridge STP timers allows a use-after-free when deleting a bridge, potentially leading to code execution or denial of service.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-72389, DEBIAN-CVE-2026-72389, GHSA-7jq5-5rp7-v6gf, UBUNTU-CVE-2026-72389

## What is CVE-2026-72389?

CVE-2026-72389 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

bridge: stp: Fix a potential use-after-free when deleting a bridge

The three STP timers are not supposed to be armed while the bridge is
administratively down. They are synchronously deactivated when the
bridge is put administratively down and the various call sites check for
'IFF_UP' before arming them.

This check is missing from br_topology_change_detection() and it is
possible to engineer a situation in which the topology change timer is
armed while the bridge is administratively down, resulting in a
use-after-free [1] when the bridge is deleted.

Fix by adding the missing check and for good measures synchronously
shutdown the three timers when the bridge is deleted.

[1]
ODEBUG: free active (active state 0) object: ffff88811662b9b0 object type: timer_list hint: br_topology_change_timer_expired (net/bridge/br_stp_timer.c:120)
WARNING: lib/debugobjects.c:629 at debug_print_object+0x1bc/0x450, CPU#9: ip/359

## Which versions are affected by CVE-2026-72389?


## How do I fix CVE-2026-72389?

Apply the vendor's patch.

## Is CVE-2026-72389 being exploited?

There is no known exploitation of CVE-2026-72389 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72389 and fix it if it is affected.

What it is: CVE-2026-72389 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72389 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-72389/ (Markdown: https://insights.sbomify.com/CVE-2026-72389/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72389
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72389
- OSV: https://osv.dev/vulnerability/CVE-2026-72389

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72389/
Summaries are generated and may contain mistakes; the official description above is the record.