# CVE-2026-93125: bpf: Reject rdonly/rdwr_buf_size kfunc arguments that exceed u32 max

> A missing bounds check in the Linux kernel BPF verifier allows integer truncation, potentially leading to memory corruption and privilege escalation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-101876, BELL-CVE-2026-93125, DEBIAN-CVE-2026-93125, GHSA-vqq3-2x9h-9pmg, UBUNTU-CVE-2026-93125

## What is CVE-2026-93125?

CVE-2026-93125 is a high-severity vulnerability in Linux, published on 17 Sep 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: Reject rdonly/rdwr_buf_size kfunc arguments that exceed u32 max

check_kfunc_args() detects a kfunc argument named rdonly_buf_size or
rdwr_buf_size and stores reg->var_off.value into meta->r0_size, a u64,
and does not bound it. check_kfunc_call() later copies that value into
the returned register's mem_size field:

  meta->r0_size = reg->var_off.value;
  ...
  regs[BPF_REG_0].mem_size = meta.r0_size;

regs[BPF_REG_0].mem_size is u32. A constant whose upper 32 bits are set
gets truncated instead of causing a load-time rejection, so the verifier
records a PTR_TO_MEM register with an approximately 4 GiB mem_size for
whatever allocation the kfunc returned. A later access check against
that register uses the truncated, wrong bound.

Reject rdonly_buf_size/rdwr_buf_size values that exceed U32_MAX at the
point meta->r0_size is set.

## Which versions are affected by CVE-2026-93125?


## How do I fix CVE-2026-93125?

Apply the vendor's patch.

## Is CVE-2026-93125 being exploited?

There is no known exploitation of CVE-2026-93125 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93125 and fix it if it is affected.

What it is: CVE-2026-93125 is a high-severity vulnerability in Linux, published on 17 Sep 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-2026-93125 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-2026-93125/ (Markdown: https://insights.sbomify.com/CVE-2026-93125/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93125
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93125
- OSV: https://osv.dev/vulnerability/CVE-2026-93125

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93125/
Summaries are generated and may contain mistakes; the official description above is the record.