# CVE-2026-97944: x86/cfi: Fix FineIBT hash offset in cfi_get_func_hash()

> A kernel bug causes a crash when BPF struct_ops programs are used with FineIBT enabled, requiring local access to trigger.

- **Severity:** Not scored
- **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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-97944, DEBIAN-CVE-2026-97944, GHSA-7jp9-pjx7-g496, UBUNTU-CVE-2026-97944

## What is CVE-2026-97944?

CVE-2026-97944 is a denial of service vulnerability in Linux, published on 25 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:

x86/cfi: Fix FineIBT hash offset in cfi_get_func_hash()

The switch of the FineIBT preamble from "subl $hash, %r10d" to the
shorter "subl $hash, %eax" moved the hash immediate from offset 7 to
offset 5 of the preamble. fineibt_preamble_hash was updated to match,
but the open-coded offset in cfi_get_func_hash() was missed and it
still reads the hash at offset 7.

cfi_get_func_hash() is used by the BPF JIT to give a struct_ops
trampoline the CFI hash of the stub function it stands in for. With
FineIBT the trampoline now gets the upper half of the real hash
followed by the first two bytes of the next instruction, so the first
indirect call from the kernel into a struct_ops program,
tcp_init_congestion_control() calling ->init() of a BPF congestion
control for example, fails the FineIBT check and the kernel dies with
a CFI failure.

Move the FineIBT preamble template and its offset defines above
cfi_get_func_hash() and use fineibt_preamble_hash there, so every
reader of the preamble shares one definition of its layout. The
CFI_FINEIBT arm is only built with CONFIG_FINEIBT, the only
configuration in which cfi_mode can take that value.
cfi_get_func_arity() does not need the same treatment: the __bhi_args
call whose displacement it reads still ends at the function address.

## Which versions are affected by CVE-2026-97944?


## How do I fix CVE-2026-97944?

Apply the vendor's patch.

## Is CVE-2026-97944 being exploited?

There is no known exploitation of CVE-2026-97944 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97944 and fix it if it is affected.

What it is: CVE-2026-97944 is a denial of service vulnerability in Linux, published on 25 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-2026-97944 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-2026-97944/ (Markdown: https://insights.sbomify.com/CVE-2026-97944/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97944
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97944
- OSV: https://osv.dev/vulnerability/CVE-2026-97944

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97944/
Summaries are generated and may contain mistakes; the official description above is the record.