# CVE-2026-93226: ipv6: use RCU iterator to dump route exceptions

> A race condition in the Linux kernel IPv6 route exception dumping allows local attackers to cause a denial of service via concurrent network updates.

- **Severity:** Not scored
- **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:** 24 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-93226, DEBIAN-CVE-2026-93226, GHSA-wvgv-43w8-m5vv, UBUNTU-CVE-2026-93226

## What is CVE-2026-93226?

CVE-2026-93226 is a vulnerability in Linux, published on 24 Sep 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:

ipv6: use RCU iterator to dump route exceptions

rt6_nh_dump_exceptions() uses hlist_for_each_entry() to iterate over
RCU-protected exception lists. The caller holds rcu_read_lock(), but does
not hold rt6_exception_lock, so rt6_insert_exception() can concurrently
add an entry with hlist_add_head_rcu().

KCSAN reports this race (irrelevant details omitted):

  ==================================================================
  BUG: KCSAN: data-race in rt6_insert_exception / rt6_nh_dump_exceptions

  write (marked) to 0xffff8a7c44c59620 of 8 bytes by interrupt on cpu 5:
    rt6_insert_exception+0x3bb/0x760
    __ip6_rt_update_pmtu+0x4fe/0x750
    ip6_sk_update_pmtu+0x19a/0x3b0
    udpv6_err+0x3ff/0x800
    icmpv6_notify+0x1e1/0x440
    icmpv6_rcv+0x8c0/0xab0
    ip6_protocol_deliver_rcu+0x616/0x840
    ip6_input_finish+0xb9/0x160
    ...
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

  read to 0xffff8a7c44c59620 of 8 bytes by task 549 on cpu 14:
    rt6_nh_dump_exceptions+0xb3/0x260
    rt6_dump_route+0x53e/0x5f0
    fib6_dump_node+0x6d/0xf0
    fib6_walk_continue+0x290/0x2d0
    fib6_dump_table+0x28d/0x360
    inet6_dump_fib+0x37d/0x620
    rtnl_dumpit+0x7b/0xd0
    netlink_dump+0x3ae/0x7e0
    ...
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

  4 locks held by dumper/549:
    ...
    #1: (rcu_read_lock){....}-{1:3}, at: inet6_dump_fib+0x88/0x620
    #2: (&tb->tb6_lock){+.-.}-{3:3}, at: fib6_dump_table+0x1e9/0x360
    #3: (rcu_read_lock){....}-{1:3}, at: rt6_dump_route+0x483/0x5f0

  value changed: 0xffff8a7c44e05700 -> 0xffff8a7c45d60100

  Reported by Kernel Concurrency Sanitizer on:
  CPU: 14 UID: 0 PID: 549 Comm: dumper Not tainted
  7.2.0-rc7-virtme #38 PREEMPT(lazy)
  ...

Use hlist_for_each_entry_rcu() to safely iterate over the exception list.

## Which versions are affected by CVE-2026-93226?


## How do I fix CVE-2026-93226?

Apply the vendor's patch.

## Is CVE-2026-93226 being exploited?

There is no known exploitation of CVE-2026-93226 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93226 and fix it if it is affected.

What it is: CVE-2026-93226 is a vulnerability in Linux, published on 24 Sep 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-2026-93226 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-2026-93226/ (Markdown: https://insights.sbomify.com/CVE-2026-93226/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93226
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93226
- OSV: https://osv.dev/vulnerability/CVE-2026-93226

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93226/
Summaries are generated and may contain mistakes; the official description above is the record.