# CVE-2026-23173: net/mlx5e: TC, delete flows only for existing peers

> A null pointer dereference in the Mellanox mlx5e driver causes a kernel crash when deleting traffic control flows for non-existent peers.

- **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:** 14 Feb 2026
- **Updated:** 11 May 2026
- **Also known as:** AZL-77742, BELL-CVE-2026-23173, DEBIAN-CVE-2026-23173, GHSA-5vr5-28pm-p634, ROOT-OS-UBUNTU-2404-CVE-2026-23173, UBUNTU-CVE-2026-23173

## What is CVE-2026-23173?

CVE-2026-23173 is a medium-severity vulnerability in Linux kernel, published on 14 Feb 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:

net/mlx5e: TC, delete flows only for existing peers

When deleting TC steering flows, iterate only over actual devcom
peers instead of assuming all possible ports exist. This avoids
touching non-existent peers and ensures cleanup is limited to
devices the driver is currently connected to.

 BUG: kernel NULL pointer dereference, address: 0000000000000008
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0002) - not-present page
 PGD 133c8a067 P4D 0
 Oops: Oops: 0002 [#1] SMP
 CPU: 19 UID: 0 PID: 2169 Comm: tc Not tainted 6.18.0+ #156 NONE
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
 RIP: 0010:mlx5e_tc_del_fdb_peers_flow+0xbe/0x200 [mlx5_core]
 Code: 00 00 a8 08 74 a8 49 8b 46 18 f6 c4 02 74 9f 4c 8d bf a0 12 00 00 4c 89 ff e8 0e e7 96 e1 49 8b 44 24 08 49 8b 0c 24 4c 89 ff <48> 89 41 08 48 89 08 49 89 2c 24 49 89 5c 24 08 e8 7d ce 96 e1 49
 RSP: 0018:ff11000143867528 EFLAGS: 00010246
 RAX: 0000000000000000 RBX: dead000000000122 RCX: 0000000000000000
 RDX: ff11000143691580 RSI: ff110001026e5000 RDI: ff11000106f3d2a0
 RBP: dead000000000100 R08: 00000000000003fd R09: 0000000000000002
 R10: ff11000101c75690 R11: ff1100085faea178 R12: ff11000115f0ae78
 R13: 0000000000000000 R14: ff11000115f0a800 R15: ff11000106f3d2a0
 FS:  00007f35236bf740(0000) GS:ff110008dc809000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000008 CR3: 0000000157a01001 CR4: 0000000000373eb0
 Call Trace:
  <TASK>
  mlx5e_tc_del_flow+0x46/0x270 [mlx5_core]
  mlx5e_flow_put+0x25/0x50 [mlx5_core]
  mlx5e_delete_flower+0x2a6/0x3e0 [mlx5_core]
  tc_setup_cb_reoffload+0x20/0x80
  fl_reoffload+0x26f/0x2f0 [cls_flower]
  ? mlx5e_tc_reoffload_flows_work+0xc0/0xc0 [mlx5_core]
  ? mlx5e_tc_reoffload_flows_work+0xc0/0xc0 [mlx5_core]
  tcf_block_playback_offloads+0x9e/0x1c0
  tcf_block_unbind+0x7b/0xd0
  tcf_block_setup+0x186/0x1d0
  tcf_block_offload_cmd.isra.0+0xef/0x130
  tcf_block_offload_unbind+0x43/0x70
  __tcf_block_put+0x85/0x160
  ingress_destroy+0x32/0x110 [sch_ingress]
  __qdisc_destroy+0x44/0x100
  qdisc_graft+0x22b/0x610
  tc_get_qdisc+0x183/0x4d0
  rtnetlink_rcv_msg+0x2d7/0x3d0
  ? rtnl_calcit.isra.0+0x100/0x100
  netlink_rcv_skb+0x53/0x100
  netlink_unicast+0x249/0x320
  ? __alloc_skb+0x102/0x1f0
  netlink_sendmsg+0x1e3/0x420
  __sock_sendmsg+0x38/0x60
  ____sys_sendmsg+0x1ef/0x230
  ? copy_msghdr_from_user+0x6c/0xa0
  ___sys_sendmsg+0x7f/0xc0
  ? ___sys_recvmsg+0x8a/0xc0
  ? __sys_sendto+0x119/0x180
  __sys_sendmsg+0x61/0xb0
  do_syscall_64+0x55/0x640
  entry_SYSCALL_64_after_hwframe+0x4b/0x53
 RIP: 0033:0x7f35238bb764
 Code: 15 b9 86 0c 00 f7 d8 64 89 02 b8 ff ff ff ff eb bf 0f 1f 44 00 00 f3 0f 1e fa 80 3d e5 08 0d 00 00 74 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 4c c3 0f 1f 00 55 48 89 e5 48 83 ec 20 89 55
 RSP: 002b:00007ffed4c35638 EFLAGS: 00000202 ORIG_RAX: 000000000000002e
 RAX: ffffffffffffffda RBX: 000055a2efcc75e0 RCX: 00007f35238bb764
 RDX: 0000000000000000 RSI: 00007ffed4c356a0 RDI: 0000000000000003
 RBP: 00007ffed4c35710 R08: 0000000000000010 R09: 00007f3523984b20
 R10: 0000000000000004 R11: 0000000000000202 R12: 00007ffed4c35790
 R13: 000000006947df8f R14: 000055a2efcc75e0 R15: 00007ffed4c35780

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-23173?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23173?

Apply the vendor's patch.

## Is CVE-2026-23173 being exploited?

There is no known exploitation of CVE-2026-23173 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-2026-23173 and fix it if it is affected.

What it is: CVE-2026-23173 is a medium-severity vulnerability in Linux kernel, published on 14 Feb 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-2026-23173 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-2026-23173/ (Markdown: https://insights.sbomify.com/CVE-2026-23173/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23173
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23173
- OSV: https://osv.dev/vulnerability/CVE-2026-23173

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23173/
Summaries are generated and may contain mistakes; the official description above is the record.