# CVE-2026-72423: bpf: Guard conntrack opts error writes

CVE-2026-72423 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-72423, released August 15, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-72423
- Priority: High
- CVSS: 8.8 (Moderate)
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 15, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-72423

## Description

In the Linux kernel, the following vulnerability has been resolved:  bpf: Guard conntrack opts error writes  The conntrack lookup and allocation kfuncs take an opts pointer together with an opts__sz argument. The verifier checks only the memory range described by opts__sz, but the wrappers unconditionally write opts->error whenever the internal lookup or allocation helper returns an error.  For an invalid size smaller than the end of opts->error, that write can land outside the verifier-checked range. Keep returning NULL for invalid arguments, but only report the error through opts->error when the supplied size includes the field.  This preserves error reporting for the supported 12-byte and 16-byte layouts, and for other invalid sizes that still include opts->error.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.115-2 | [DEBIAN-CVE-2026-72423](https://patchblox.com/security/data/fix/linux/debian-cve-2026-72423.md) | Aug 15, 2026 |
| Linux | linux Debian 14 | 7.1.5-1 | [DEBIAN-CVE-2026-72423](https://patchblox.com/security/data/fix/linux/debian-cve-2026-72423.md) | Aug 15, 2026 |

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Data as of 2026-11-09T13:31:49Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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