# CVE-2026-80986: net/smc: bound the peer rkey counts in SMC-Rv2 LLC messages

> A slab-out-of-bounds read in the Linux kernel's SMC-Rv2 LLC message handling can cause a system crash when processing link additions.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-80986, DEBIAN-CVE-2026-80986, GHSA-f5q8-wrwg-4pwh, UBUNTU-CVE-2026-80986

## What is CVE-2026-80986?

CVE-2026-80986 is a critical memory corruption vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

net/smc: bound the peer rkey counts in SMC-Rv2 LLC messages

On a link whose device has max_recv_sge == 1 there is no shared v2 receive
buffer, and smc_llc_save_add_link_rkeys() takes the v2 extension from 44
bytes past the start of the queue entry's inline message:

  ext = (struct smc_llc_msg_add_link_v2_ext *)(llc_msg + SMC_WR_TX_SIZE);

The entry is a 72-byte allocation and the extension starts at offset 68, so
ext->num_rkeys at offset 94 is already past it. This happens on every
SMC-Rv2 link addition, whatever the peer sends:

  [    2.490065] BUG: KASAN: slab-out-of-bounds in smc_llc_save_add_link_rkeys+0x333/0x350
  [    2.490431] Read of size 2 at addr ffff8880056406de by task smctest/106
  [    2.490709]
  [    2.490792] CPU: 0 UID: 0 PID: 106 Comm: smctest Not tainted 7.2.0-rc5-p1-g77a5d9d9c99f #32 PREEMPT(lazy)
  [    2.490795] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
  [    2.490798] Call Trace:
  [    2.490803]  <TASK>
  [    2.490805]  dump_stack_lvl+0x53/0x70
  [    2.490810]  print_report+0xd0/0x630
  [    2.490828]  ? __pfx__raw_spin_lock_irqsave+0x10/0x10
  [    2.490832]  ? smc_llc_save_add_link_rkeys+0x333/0x350
  [    2.490834]  kasan_report+0xce/0x100
  [    2.490836]  ? smc_llc_save_add_link_rkeys+0x333/0x350
  [    2.490837]  smc_llc_save_add_link_rkeys+0x333/0x350
  [    2.490839]  ? smcr_buf_map_lgr+0x1bf/0x2b0
  [    2.490844]  smc_llc_cli_add_link+0xca7/0x1e80
  [    2.490848]  ? smc_llc_wait+0x355/0x810
  [    2.490850]  ? __pfx_smc_llc_wait+0x10/0x10
  [    2.490851]  ? __pfx_smc_llc_cli_add_link+0x10/0x10
  [    2.490853]  ? __pfx_autoremove_wake_function+0x10/0x10
  [    2.490863]  __smc_connect+0x3f5c/0x4980
  [    2.490873]  ? __pfx_kernel_connect+0x10/0x10
  [    2.490888]  ? __pfx___smc_connect+0x10/0x10
  [    2.490891]  ? release_sock+0x148/0x1d0
  [    2.490894]  smc_connect+0x42c/0x580
  [    2.490896]  __sys_connect+0xfc/0x130
  [    2.490898]  ? __pfx___sys_connect+0x10/0x10
  [    2.490900]  ? handle_mm_fault+0x1a1/0x430
  [    2.490908]  __x64_sys_connect+0x6d/0xb0
  [    2.490909]  ? fpregs_assert_state_consistent+0x56/0xe0
  [    2.490917]  do_syscall_64+0xf9/0x540
  [    2.490921]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
  [    2.490924] RIP: 0033:0x421bb4
  [    2.490927] Code: ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d ad 34 09 00 00 74 13 b8 2a 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 4c c3 0f 1f 00 55 48 89 e5 48 83 ec 10 89 55
  [    2.490929] RSP: 002b:00007ffd473b01a8 EFLAGS: 00000202 ORIG_RAX: 000000000000002a
  [    2.490935] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000421bb4
  [    2.490936] RDX: 0000000000000010 RSI: 00007ffd473b01d0 RDI: 0000000000000003
  [    2.490937] RBP: 0000000000003930 R08: 0000000000000004 R09: 0000000000000000
  [    2.490938] R10: 00007ffd473b0f98 R11: 0000000000000202 R12: 0000000000000006
  [    2.490939] R13: 00007ffd473b0f87 R14: 0000000000000003 R15: 00007ffd473b0f90
  [    2.490940]  </TASK>
  [    2.490941]
  [    2.499545] Allocated by task 44:
  [    2.499693]  kasan_save_stack+0x33/0x60
  [    2.499860]  kasan_save_track+0x14/0x30
  [    2.500026]  __kasan_kmalloc+0x8f/0xa0
  [    2.500190]  __kmalloc_cache_noprof+0x158/0x370
  [    2.500393]  smc_llc_enqueue+0x72/0x560
  [    2.500559]  smc_wr_rx_tasklet_fn+0x474/0xa80
  [    2.500747]  tasklet_action_common+0x20f/0x8a0
  [    2.500945]  handle_softirqs+0x18e/0x590
  [    2.501115]  do_softirq+0x3b/0x60
  [    2.501266]  __local_bh_enable_ip+0x61/0x70
  [    2.501446]  __alloc_skb+0x732/0x890
  [    2.501604]  rxe_init_packet+0x16b/0x4f0
  [    2.501783]  prepare_ack_packet+0xb8/0x830
  [    2.501962]  rxe_receiver+0x495/0x96e0
  [    2.502125]  do_work+0x144/0x470
  [    2.502269]  process_one_work+0x633/0x1030
  [    2.502450]  worker_thread+0x45b/0xd10
  [    2.50261
---truncated---

## Which versions are affected by CVE-2026-80986?


## How do I fix CVE-2026-80986?

Apply the vendor's patch.

## Is CVE-2026-80986 being exploited?

There is no known exploitation of CVE-2026-80986 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80986 and fix it if it is affected.

What it is: CVE-2026-80986 is a critical memory corruption vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-80986 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-2026-80986/ (Markdown: https://insights.sbomify.com/CVE-2026-80986/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80986
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80986
- OSV: https://osv.dev/vulnerability/CVE-2026-80986

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80986/
Summaries are generated and may contain mistakes; the official description above is the record.