# CVE-2026-53134: netfilter: nft_fib: fix stale stack leak via the OIFNAME register

> A local attacker can leak uninitialized kernel stack memory to userspace via the netfilter nft_fib module's OIFNAME register handling.

- **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:** 25 Jun 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-90527, BELL-CVE-2026-53134, DEBIAN-CVE-2026-53134, GHSA-5wp9-x843-xmxf, ROOT-OS-DEBIAN-11-CVE-2026-53134, ROOT-OS-DEBIAN-12-CVE-2026-53134, ROOT-OS-UBUNTU-2204-CVE-2026-53134, ROOT-OS-UBUNTU-2404-CVE-2026-53134, UBUNTU-CVE-2026-53134

## What is CVE-2026-53134?

CVE-2026-53134 is a medium-severity vulnerability in Linux kernel, published on 25 Jun 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:

netfilter: nft_fib: fix stale stack leak via the OIFNAME register

For NFT_FIB_RESULT_OIFNAME the destination register is declared with
len = IFNAMSIZ (four 32-bit registers), but on the lookup-fail,
RTN_LOCAL and oif-mismatch paths nft_fib{4,6}_eval() only writes one
register via "*dest = 0". The remaining three registers are left as
whatever was on the stack in nft_do_chain()'s struct nft_regs, and a
downstream expression that loads the register span can leak that
uninitialised kernel stack to userspace.

The NFTA_FIB_F_PRESENT existence check has the same shape: it is only
meaningful for NFT_FIB_RESULT_OIF, yet it was accepted for any result type
while the eval stores a single byte via nft_reg_store8(), leaving the rest
of the declared span stale.

Fix both:

 - replace the bare "*dest = 0" in the eval with nft_fib_store_result(),
   which strscpy_pad()s the whole IFNAMSIZ for OIFNAME (and is already
   used on the other early-return path), and

 - restrict NFTA_FIB_F_PRESENT to NFT_FIB_RESULT_OIF and declare its
   destination as a single u8, so the marked span matches the one byte
   the eval writes.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-53134?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53134?

Apply the vendor's patch.

## Is CVE-2026-53134 being exploited?

There is no known exploitation of CVE-2026-53134 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-2026-53134 and fix it if it is affected.

What it is: CVE-2026-53134 is a medium-severity vulnerability in Linux kernel, published on 25 Jun 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-2026-53134 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-2026-53134/ (Markdown: https://insights.sbomify.com/CVE-2026-53134/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53134
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53134
- OSV: https://osv.dev/vulnerability/CVE-2026-53134

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53134/
Summaries are generated and may contain mistakes; the official description above is the record.