# CVE-2024-26893: firmware: arm_scmi: Fix double free in SMC transport cleanup path

> A double free vulnerability in the Linux kernel's SCMI SMC transport cleanup path can cause a NULL pointer dereference and 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:** 17 Apr 2024
- **Updated:** 11 May 2026
- **Also known as:** AZL-55971, BELL-CVE-2024-26893, DEBIAN-CVE-2024-26893, GHSA-g64m-m7r3-j854, ROOT-OS-DEBIAN-11-CVE-2024-26893, UBUNTU-CVE-2024-26893

## What is CVE-2024-26893?

CVE-2024-26893 is a medium-severity use after free vulnerability in Linux kernel, published on 17 Apr 2024. 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:

firmware: arm_scmi: Fix double free in SMC transport cleanup path

When the generic SCMI code tears down a channel, it calls the chan_free
callback function, defined by each transport. Since multiple protocols
might share the same transport_info member, chan_free() might want to
clean up the same member multiple times within the given SCMI transport
implementation. In this case, it is SMC transport. This will lead to a NULL
pointer dereference at the second time:

    | scmi_protocol scmi_dev.1: Enabled polling mode TX channel - prot_id:16
    | arm-scmi firmware:scmi: SCMI Notifications - Core Enabled.
    | arm-scmi firmware:scmi: unable to communicate with SCMI
    | Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
    | Mem abort info:
    |   ESR = 0x0000000096000004
    |   EC = 0x25: DABT (current EL), IL = 32 bits
    |   SET = 0, FnV = 0
    |   EA = 0, S1PTW = 0
    |   FSC = 0x04: level 0 translation fault
    | Data abort info:
    |   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
    |   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
    |   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
    | user pgtable: 4k pages, 48-bit VAs, pgdp=0000000881ef8000
    | [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
    | Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
    | Modules linked in:
    | CPU: 4 PID: 1 Comm: swapper/0 Not tainted 6.7.0-rc2-00124-g455ef3d016c9-dirty #793
    | Hardware name: FVP Base RevC (DT)
    | pstate: 61400009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
    | pc : smc_chan_free+0x3c/0x6c
    | lr : smc_chan_free+0x3c/0x6c
    | Call trace:
    |  smc_chan_free+0x3c/0x6c
    |  idr_for_each+0x68/0xf8
    |  scmi_cleanup_channels.isra.0+0x2c/0x58
    |  scmi_probe+0x434/0x734
    |  platform_probe+0x68/0xd8
    |  really_probe+0x110/0x27c
    |  __driver_probe_device+0x78/0x12c
    |  driver_probe_device+0x3c/0x118
    |  __driver_attach+0x74/0x128
    |  bus_for_each_dev+0x78/0xe0
    |  driver_attach+0x24/0x30
    |  bus_add_driver+0xe4/0x1e8
    |  driver_register+0x60/0x128
    |  __platform_driver_register+0x28/0x34
    |  scmi_driver_init+0x84/0xc0
    |  do_one_initcall+0x78/0x33c
    |  kernel_init_freeable+0x2b8/0x51c
    |  kernel_init+0x24/0x130
    |  ret_from_fork+0x10/0x20
    | Code: f0004701 910a0021 aa1403e5 97b91c70 (b9400280)
    | ---[ end trace 0000000000000000 ]---

Simply check for the struct pointer being NULL before trying to access
its members, to avoid this situation.

This was found when a transport doesn't really work (for instance no SMC
service), the probe routines then tries to clean up, and triggers a crash.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2024-26893?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-26893?

Apply the vendor's patch.

## Is CVE-2024-26893 being exploited?

There is no known exploitation of CVE-2024-26893 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-2024-26893 and fix it if it is affected.

What it is: CVE-2024-26893 is a medium-severity use after free vulnerability in Linux kernel, published on 17 Apr 2024. 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-2024-26893 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-2024-26893/ (Markdown: https://insights.sbomify.com/CVE-2024-26893/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-26893
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-26893
- OSV: https://osv.dev/vulnerability/CVE-2024-26893

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-26893/
Summaries are generated and may contain mistakes; the official description above is the record.