# CVE-2026-72028: riscv: probes: save original sp in rethook trampoline

> A local attacker with high privileges can crash the Linux kernel on RISC-V by triggering a kretprobe that reads from an invalid stack pointer.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72028, DEBIAN-CVE-2026-72028, GHSA-rj58-8r73-76rg, UBUNTU-CVE-2026-72028

## What is CVE-2026-72028?

CVE-2026-72028 is a denial of service vulnerability in Linux, published on 15 Aug 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:

riscv: probes: save original sp in rethook trampoline

Reading a word from the stack in a kretprobe crashes a risc-v kernel.

$ cd /sys/kernel/tracing/
$ echo 'r n_tty_write $stack0' > dynamic_events
$ echo 1 > events/kprobes/enable
Unable to handle kernel paging request at virtual address 0000000200000128
...
[<ffffffff80016d16>] regs_get_kernel_stack_nth+0x26/0x38
[<ffffffff80177196>] process_fetch_insn+0x3ee/0x760
[<ffffffff80177836>] kretprobe_trace_func+0x116/0x1f0
[<ffffffff8017795a>] kretprobe_dispatcher+0x4a/0x58
[<ffffffff8013572e>] kretprobe_rethook_handler+0x5e/0x90
[<ffffffff80180838>] rethook_trampoline_handler+0x70/0x108
[<ffffffff8001ba32>] arch_rethook_trampoline_callback+0x12/0x1c
[<ffffffff8001ba84>] arch_rethook_trampoline+0x48/0x94
[<ffffffff8067872a>] tty_write+0x1a/0x30

In regs_get_kernel_stack_nth, regs->sp contains an arbitrary value.

arch_rethook_trampoline saves the registers from the probed function in a
struct pt_regs. sp is not saved. Instead, sp is decremented for
arch_rethook_trampoline's local stack.

Fix this crash and save the original sp along with the other registers.
Use a0 as a temporary register, it is overwritten anyway.

[pjw@kernel.org: added Fixes tag; cc'ed stable]

## Which versions are affected by CVE-2026-72028?


## How do I fix CVE-2026-72028?

Apply the vendor's patch.

## Is CVE-2026-72028 being exploited?

There is no known exploitation of CVE-2026-72028 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72028 and fix it if it is affected.

What it is: CVE-2026-72028 is a denial of service vulnerability in Linux, published on 15 Aug 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-2026-72028 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-2026-72028/ (Markdown: https://insights.sbomify.com/CVE-2026-72028/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72028
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72028
- OSV: https://osv.dev/vulnerability/CVE-2026-72028

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72028/
Summaries are generated and may contain mistakes; the official description above is the record.