# CVE-2026-90195: riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args

CVE-2026-90195 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-90195, released September 23, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-90195
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 17, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-90195

## Description

In the Linux kernel, the following vulnerability has been resolved:  riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args  On RV64, the ABI requires sign-extension for signed 1-byte and 2-byte kfunc args. However, the RV64 JIT currently does not perform sign-extension for such kfunc args.  Before commit 7ce090afbf72 ("bpf: Infer zext_dst based on static register liveness analysis"), state pruning could potentially omit zero-extension of 32-bit subregisters, which inadvertently masked the above issue by making the args appear as if they had been properly sign-extended. After that commit, the problem is exposed, causing the kfunc_call/kfunc_call_test4 selftest to fail.  Fix this by extending the existing sign-extension logic to handle signed 1-byte and 2-byte kfunc args as well.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.111-1 | [DEBIAN-CVE-2026-90195](https://patchblox.com/security/data/fix/linux/debian-cve-2026-90195.md) | Sep 23, 2026 |
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-90195](https://patchblox.com/security/data/fix/linux/debian-cve-2026-90195.md) | Sep 23, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.111-1~deb12u1 | [DEBIAN-CVE-2026-90195](https://patchblox.com/security/data/fix/linux/debian-cve-2026-90195.md) | Sep 23, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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