Listen to this Post
How CVE-2026-43390 Works:
The vulnerability resides in the Linux kernel’s `nstree` component, specifically within the `listns()` function, which handles the listing of namespaces. The core issue is an insufficient granularity of access control (CWE-1220). The original `listns()` function only checks if the caller possesses the global `CAP_SYS_ADMIN` capability to list all namespaces on the system. It does not verify if the caller owns the namespaces it is trying to view.
A privileged process (like a container or service) is given `CAP_SYS_ADMIN` within its own context. Under the flawed logic, this process could list and gather detailed information about the namespaces of other different privileged services on the same host. This includes sensitive data like process relationships, network configurations, and mount points.
The vulnerability was introduced in kernel version 6.19 with commit 76b6f5dfb3fd. The fix replaces the old, overly permissive logic with a new `may_see_all_namespaces()` helper function. This helper centralizes the policy for determining whether a process can view all namespaces or only its own. By default, even privileged processes are now restricted to viewing only their own namespaces, preventing them from enumerating other services’ namespaces and leaking sensitive information. The fix effectively enforces a “need-to-know” principle for namespace information among privileged services.
DailyCVE Form:
Platform: Linux Kernel
Version: Up to 6.19.8
Vulnerability : Information Disclosure
Severity: Medium
date: 2026-05-08
Prediction: 2026-06-30
What Undercode Say:
The vulnerability is in the `listns()` function. We can simulate old vs. new behavior by analyzing the `may_see_all_namespaces()` check. An attacker would look for an arbitrary read via /proc/
/ns/</code>. [bash] Check vulnerable kernels (affected versions up to 6.19.8) uname -r List all namespaces (requires CAP_SYS_ADMIN before patch) sudo lsns Inspect a service's namespaces sudo ls -la /proc/[bash]/ns/ Check for fixes by looking at the kernel commit sudo dmesg | grep -i "nstree"
How Exploit:
The flaw allows a privileged attacker or malicious container to enumerate all host namespaces, leaking process IDs, network configurations, and mount points of other tenants. No public exploit exists; exploitation is trivial via `lsns` on vulnerable kernels.
Protection from this CVE:
Upgrade to Linux kernel version 6.19.9, 7.0, or any later release. Apply the specific kernel patches `0abd81645fc95ec6a9d4e4813000f22c5efc0ff4` or 8d76afe84fa2babf604b3c173730d4d2b067e361. As a workaround, restrict capabilities for privileged containers and enforce strict SELinux/AppArmor policies.
Impact:
A malicious privileged process can view namespaces of other services, leaking sensitive configuration and state information, breaking isolation between tenants on shared infrastructure.
🎯Let’s Practice Exploiting & Learn Patching For Free:
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
🎓 Live Courses & Certifications:
Join Undercode Academy for Verified Certifications
🚀 Request a Custom Project:
Secure, high-velocity infrastructure and disruptive technological engineering. Contact our engineering team for high-tier development and proprietary systems:
[email protected]