OSG-SEC-2026-07-30 Linux Kernel Network Scheduler Vulnerability

Dear OSG Security Contacts,

A flaw was found in the Linux kernel's networking scheduler (CVE-2026-53264) [1]. A race condition can lead to a Use-After-Free (UAF) vulnerability which could potentially allow an attacker to cause system instability or execute arbitrary code. Publicly available research has demonstrated a working proof-of-concept exploit that can achieve root privileges on vulnerable systems.

WHAT ARE THE VULNERABILITIES:

A flaw exists in the Linux kernel's traffic control (net/sched) subsystem due to a use-after-free race condition when traffic control filter actions are created and deleted concurrently [4]. Under specific timing conditions, the kernel may access an object after it has been freed, resulting in kernel memory corruption. According to publicly available research [9], this flaw can be leveraged to achieve local privilege escalation on vulnerable systems.

IMPACTED VERSIONS:

Red Hat Enterprise Linux
RHEL 7,8,9 and 10 are affected [1].

Debian
Security updates are available for some releases. See reference [2] for more details.

Ubuntu
Apply updates as they become available.

MITIGATION

The published proof-of-concept exploit relies on unprivileged network namespaces. Sites that do not require this functionality may consider disabling unprivileged network namespaces as a temporary mitigation [6] [7].

WHAT YOU SHOULD DO:

Apply vendor-provided kernel updates addressing CVE-2026-53264 as soon as they become available. A system reboot is required after installing the updated kernel for the fix to take effect. Prioritize systems that provide access to unprivileged users. As a temporary mitigation, sites that do not require unprivileged network namespaces may consider disabling them to prevent the currently published exploitation technique. This is not a substitute for installing the vendor-provided kernel update.

REFERENCES

[1] https://access.redhat.com/security/cve/cve-2026-53264
[2] https://security-tracker.debian.org/tracker/CVE-2026-53264
[3] https://ubuntu.com/security/CVE-2026-53264
[4] https://bugzilla.redhat.com/show_bug.cgi?id=2492851. [5] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5057e1aca011e51ef51498c940ef96f3d3e8a305
[6] https://csirt.egi.eu/2022/10/19/linux-namespaces-and-containers/
[7] https://apptainer.org/docs/admin/main/user_namespace.html#disabling-network-namespaces
[8] https://www.egi.eu/
[9] https://thehackernews.com/2026/07/researcher-says-ai-helped-develop-linux.html

Please contact the OSG security team at [email protected] if you have any questions or concerns.

OSG Security Team