# CVE-2026-93127: bpf: Drop scalar id on sign-extending narrowing stack fills

> A flaw in the Linux kernel BPF verifier allows out-of-bounds memory access due to incorrect scalar ID handling during sign-extending loads, potentially enabling 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:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-93127, GHSA-6crf-588f-8r2f, UBUNTU-CVE-2026-93127

## What is CVE-2026-93127?

CVE-2026-93127 is a high-severity memory corruption 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: Drop scalar id on sign-extending narrowing stack fills

When a spilled scalar is filled back with a sign-extending narrowing load
(BPF_MEMSX), check_stack_read_fixed_off() copies the spilled register
including its scalar id, but coerce_reg_to_size_sx() then sign-extends the
filled register's value. If the same slot is also filled with a plain
zero-extending load (BPF_MEM), both destination registers share the id yet
hold different values. A later 'if <zext-reg> == const' then refines the
sign-extended register through sync_linked_regs() to a value it does not
have at runtime (e.g. the verifier believes 0x80000000 while the register
is 0xffffffff80000000), which can be turned into an out-of-bounds access.

Drop the shared scalar id at the sign-extension site in check_mem_access()
when sign extension actually changes the value, mirroring the BPF_MOVSX
handling in check_alu_op() (no_sext = reg_umax < 2^(size*8-1)).

## Which versions are affected by CVE-2026-93127?


## How do I fix CVE-2026-93127?

Apply the vendor's patch.

## Is CVE-2026-93127 being exploited?

There is no known exploitation of CVE-2026-93127 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93127 and fix it if it is affected.

What it is: CVE-2026-93127 is a high-severity memory corruption 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-2026-93127 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-2026-93127/ (Markdown: https://insights.sbomify.com/CVE-2026-93127/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93127
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93127
- OSV: https://osv.dev/vulnerability/CVE-2026-93127

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93127/
Summaries are generated and may contain mistakes; the official description above is the record.