# CVE-2026-68323: tipc: serialize udp bearer replicast list updates

> A race condition in the Linux kernel TIPC UDP bearer allows unprivileged users to corrupt memory and cause a system crash.

- **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:** 10 Aug 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-95187, BELL-CVE-2026-68323, DEBIAN-CVE-2026-68323, GHSA-fwrg-j278-r47c, UBUNTU-CVE-2026-68323

## What is CVE-2026-68323?

CVE-2026-68323 is a high-severity vulnerability in Linux, published on 10 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:

tipc: serialize udp bearer replicast list updates

tipc_udp_rcast_add() and cleanup_bearer() both update ub->rcast.list with
list_add_rcu() / list_del_rcu(), but nothing serializes them. The add runs
from the encap receive softirq (via tipc_udp_rcast_disc()) without
rtnl_lock(), so it can race the cleanup delete and corrupt the list:

  list_del corruption. prev->next should be ffff8880298d7ab8,
    but was ffff88802449ad38. (prev=ffff888027e3ec98)
  kernel BUG at lib/list_debug.c:62!
  RIP: __list_del_entry_valid_or_report+0x17a/0x200
  Workqueue: events cleanup_bearer
  Call Trace:
   cleanup_bearer (net/tipc/udp_media.c:811)
   process_one_work (kernel/workqueue.c:3302)
   worker_thread (kernel/workqueue.c:3466)

The bearer can be enabled from an unprivileged user namespace, as the
TIPCv2 generic-netlink ops carry no GENL_ADMIN_PERM.

Add a spinlock to struct udp_bearer and take it around the list_add_rcu()
in tipc_udp_rcast_add() and the list_del_rcu() loop in cleanup_bearer() so
the two writers can no longer corrupt the list.

Reject a duplicate peer under the same lock before allocating, and remove
tipc_udp_is_known_peer(). The old lockless pre-check in
tipc_udp_rcast_disc() was racy: two softirqs discovering the same peer
could both find it absent and add it twice.

cleanup_bearer() runs from a workqueue after tipc_udp_disable() clears the
bearer's up bit, so an encap softirq can still reach tipc_udp_rcast_add()
and add a peer after cleanup_bearer() has already emptied the list, leaking
that entry when the bearer is freed. Mark the bearer disabled under
rcast_lock once the list is emptied and refuse further additions.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-68323?


## How do I fix CVE-2026-68323?

Apply the vendor's patch.

## Is CVE-2026-68323 being exploited?

There is no known exploitation of CVE-2026-68323 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68323 and fix it if it is affected.

What it is: CVE-2026-68323 is a high-severity vulnerability in Linux, published on 10 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-2026-68323 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-2026-68323/ (Markdown: https://insights.sbomify.com/CVE-2026-68323/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68323
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68323
- OSV: https://osv.dev/vulnerability/CVE-2026-68323

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68323/
Summaries are generated and may contain mistakes; the official description above is the record.