# CVE-2026-23405 — Linux

> As of 2026-05-11, CVE-2026-23405 is a MEDIUM-severity vulnerability in Linux, CVSS v3.1 5.5, EPSS 0.1% (7.0th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-23405, most recently “Linux Kernel LPE Surge: Copy Fail (CVE-2026-31431), Dirty Frag/Fragnesia (CVE-2026-43284/CVE-2026-43500/CVE-2026-46300), and CrackArmor AppArmor Flaws vs. Defense-in-Depth Mitigations”.

**Last updated:** 2026-05-11

## What is CVE-2026-23405?

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix: limit the number of levels of policy namespaces Currently the number of policy namespaces is not bounded relying on the user namespace limit. However policy namespaces aren't strictly tied to user namespaces and it is possible to create them and nest them arbitrarily deep which can be used to exhaust system resource. Hard cap policy namespaces to the same depth as user namespaces.

Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 207 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 5.5 — MEDIUM (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 7.0% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-04-01, last modified 2026-05-11

## Is CVE-2026-23405 being exploited?

It currently carries a trending score of 7 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [Linux](https://intel.threadlinqs.com/vendors/linux): Linux

## How to fix CVE-2026-23405

The record marks a vendor fix as available for CVE-2026-23405. Patch reference: [https://git.kernel.org/stable/c/306039414932c80f8420695a24d4fe10c84ccfb2](https://git.kernel.org/stable/c/306039414932c80f8420695a24d4fe10c84ccfb2). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

## Threat activity tracking CVE-2026-23405

1 tracked threat in the Threadlinqs corpus references CVE-2026-23405, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Linux Kernel LPE Surge: Copy Fail (CVE-2026-31431), Dirty Frag/Fragnesia (CVE-2026-43284/CVE-2026-43500/CVE-2026-46300), and CrackArmor AppArmor Flaws vs. Defense-in-Depth Mitigations](https://intel.threadlinqs.com/threat/TL-2026-2424) — HIGH · 2026-05-29

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-10-10. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [git.kernel.org](https://git.kernel.org/stable/c/6b396cc2f0365e684fc1d3547d18ef79fcee225d)
- [git.kernel.org (87d0cecc900e55d55fc4dbfb43ac93e269c7a5b3)](https://git.kernel.org/stable/c/87d0cecc900e55d55fc4dbfb43ac93e269c7a5b3)
- [git.kernel.org (b1226e37eb3754d389721c135db6107db94c7a72)](https://git.kernel.org/stable/c/b1226e37eb3754d389721c135db6107db94c7a72)
- [git.kernel.org (3f8699b3ee0c04b4b9bc27b82cd89a40e81e1d2e)](https://git.kernel.org/stable/c/3f8699b3ee0c04b4b9bc27b82cd89a40e81e1d2e)
- [git.kernel.org (853ce31ca72097d23991a06876a2ccb5cb64b603)](https://git.kernel.org/stable/c/853ce31ca72097d23991a06876a2ccb5cb64b603)

_Showing 5 of 8 recorded references._

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-23405
Full detection coverage and IOCs for threats exploiting CVE-2026-23405 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp