# CVE-2026-53034: bpf, sockmap: Fix af_unix null-ptr-deref in proto update

> A race condition in the Linux kernel's BPF sockmap implementation allows a local attacker to trigger a null pointer dereference, causing a system crash.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 24 Jun 2026
- **Updated:** 24 Jun 2026
- **Also known as:** BELL-CVE-2026-53034, DEBIAN-CVE-2026-53034, GHSA-pwx6-fvf4-6686, ROOT-OS-DEBIAN-12-CVE-2026-53034, ROOT-OS-UBUNTU-2204-CVE-2026-53034, ROOT-OS-UBUNTU-2404-CVE-2026-53034, UBUNTU-CVE-2026-53034

## What is CVE-2026-53034?

CVE-2026-53034 is a medium-severity vulnerability in Linux kernel, published on 24 Jun 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:

bpf, sockmap: Fix af_unix null-ptr-deref in proto update

unix_stream_connect() sets sk_state (`WRITE_ONCE(sk->sk_state,
TCP_ESTABLISHED)`) _before_ it assigns a peer (`unix_peer(sk) = newsk`).
sk_state == TCP_ESTABLISHED makes sock_map_sk_state_allowed() believe that
socket is properly set up, which would include having a defined peer. IOW,
there's a window when unix_stream_bpf_update_proto() can be called on
socket which still has unix_peer(sk) == NULL.

         CPU0 bpf                            CPU1 connect
         --------                            ------------

                                WRITE_ONCE(sk->sk_state, TCP_ESTABLISHED)
sock_map_sk_state_allowed(sk)
...
sk_pair = unix_peer(sk)
sock_hold(sk_pair)
                                sock_hold(newsk)
                                smp_mb__after_atomic()
                                unix_peer(sk) = newsk

BUG: kernel NULL pointer dereference, address: 0000000000000080
RIP: 0010:unix_stream_bpf_update_proto+0xa0/0x1b0
Call Trace:
  sock_map_link+0x564/0x8b0
  sock_map_update_common+0x6e/0x340
  sock_map_update_elem_sys+0x17d/0x240
  __sys_bpf+0x26db/0x3250
  __x64_sys_bpf+0x21/0x30
  do_syscall_64+0x6b/0x3a0
  entry_SYSCALL_64_after_hwframe+0x76/0x7e

Initial idea was to move peer assignment _before_ the sk_state update[1],
but that involved an additional memory barrier, and changing the hot path
was rejected.
Then a NULL check during proto update in unix_stream_bpf_update_proto() was
considered[2], but the follow-up discussion[3] focused on the root cause,
i.e. sockmap update taking a wrong lock. Or, more specifically, missing
unix_state_lock()[4].
In the end it was concluded that teaching sockmap about the af_unix locking
would be unnecessarily complex[5].
Complexity aside, since BPF_PROG_TYPE_SCHED_CLS and BPF_PROG_TYPE_SCHED_ACT
are allowed to update sockmaps, sock_map_update_elem() taking the unix
lock, as it is currently implemented in unix_state_lock():
spin_lock(&unix_sk(s)->lock), would be problematic. unix_state_lock() taken
in a process context, followed by a softirq-context TC BPF program
attempting to take the same spinlock -- deadlock[6].
This way we circled back to the peer check idea[2].

[1]: https://lore.kernel.org/netdev/ba5c50aa-1df4-40c2-ab33-a72022c5a32e@rbox.co/
[2]: https://lore.kernel.org/netdev/20240610174906.32921-1-kuniyu@amazon.com/
[3]: https://lore.kernel.org/netdev/7603c0e6-cd5b-452b-b710-73b64bd9de26@linux.dev/
[4]: https://lore.kernel.org/netdev/CAAVpQUA+8GL_j63CaKb8hbxoL21izD58yr1NvhOhU=j+35+3og@mail.gmail.com/
[5]: https://lore.kernel.org/bpf/CAAVpQUAHijOMext28Gi10dSLuMzGYh+jK61Ujn+fZ-wvcODR2A@mail.gmail.com/
[6]: https://lore.kernel.org/bpf/dd043c69-4d03-46fe-8325-8f97101435cf@linux.dev/

Summary of scenarios where af_unix/stream connect() may race a sockmap
update:

1. connect() vs. bpf(BPF_MAP_UPDATE_ELEM), i.e. sock_map_update_elem_sys()

   Implemented NULL check is sufficient. Once assigned, socket peer won't
   be released until socket fd is released. And that's not an issue because
   sock_map_update_elem_sys() bumps fd refcnf.

2. connect() vs BPF program doing update

   Update restricted per verifier.c:may_update_sockmap() to

      BPF_PROG_TYPE_TRACING/BPF_TRACE_ITER
      BPF_PROG_TYPE_SOCK_OPS (bpf_sock_map_update() only)
      BPF_PROG_TYPE_SOCKET_FILTER
      BPF_PROG_TYPE_SCHED_CLS
      BPF_PROG_TYPE_SCHED_ACT
      BPF_PROG_TYPE_XDP
      BPF_PROG_TYPE_SK_REUSEPORT
      BPF_PROG_TYPE_FLOW_DISSECTOR
      BPF_PROG_TYPE_SK_LOOKUP

   Plus one more race to consider:

            CPU0 bpf                            CPU1 connect
            --------                            ------------

                                   WRITE_ONCE(sk->sk_state, TCP_ESTABLISHED)
   sock_map_sk_state_allowed(sk)
                                   sock_hold(newsk)
                                   smp_mb__after_atomic()
                
---truncated---

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-53034?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53034?

Apply the vendor's patch.

## Is CVE-2026-53034 being exploited?

There is no known exploitation of CVE-2026-53034 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53034 and fix it if it is affected.

What it is: CVE-2026-53034 is a medium-severity vulnerability in Linux kernel, published on 24 Jun 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-2026-53034 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-53034/ (Markdown: https://insights.sbomify.com/CVE-2026-53034/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53034
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53034
- OSV: https://osv.dev/vulnerability/CVE-2026-53034

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53034/
Summaries are generated and may contain mistakes; the official description above is the record.