A new vulnerability, CVE-2025-1272, has been discovered in Fedora Linux distributions running the Linux kernel version 6.12 and above. This flaw happens because the kernel lockdown mode is unknowingly disabled by default with no warnings or notifications. As a result, Fedora users—especially those depending on Secure Boot—face significantly increased risks: attackers can bypass lockdown protections, access sensitive kernel data, and even load unsigned modules, breaking Secure Boot guarantees.

This is notable because the lockdown mode is supposed to be *on by default* when Secure Boot is in use, tightly restricting kernel functionality to prevent privilege escalation or information leaks. On Fedora, this expectation is now broken.

> Note: This issue is confirmed to affect only Fedora Linux. Other Linux distributions with kernel lockdown enabled do not appear to be affected in this way.

What’s Lockdown Mode, and Why Is it Critical?

Lockdown mode restricts the Linux kernel's capabilities to safeguard the system’s integrity—especially important in Secure Boot environments. When enabled, it limits access to kernel memory (preventing kernel rootkits from hiding), locks down debugging mechanisms like kprobes/BPF, and most importantly, stops loading unsigned (potentially malicious) kernel modules.

Key protections provided by Lockdown mode

- No reading from kernel memory (/dev/mem, /dev/kmem, /dev/port)

What Happened?

Starting with the Linux 6.12 kernel, Fedora changed some kernel build/config flags or defaults that leave Lockdown disabled, even under Secure Boot, and don’t notify the user. The issue appears whether the system boots in UEFI Secure Boot mode or not.

> Exploit Impact: Privileged users (root/admin) and attackers with root access can trivially compromise kernel integrity and extract data.

Exploit Scenario: Why This is Dangerous

Let's imagine a Secure Boot Fedora system with this vulnerability.

Attacker gains root access (via any local exploit or privilege escalation).

2. They want to load a rootkit or module that would otherwise require proper signing or lockdown bypass.

Because lockdown *is off*, the attacker can now

- Access /dev/kmem, /dev/mem, and /dev/port (read/write raw kernel memory and I/O).

`c

// Example: probe running system calls

All while Secure Boot users *think their system is protected*.

4. Secure Boot is *entirely bypassed* regarding its main goal: restricting kernel execution to trusted code.

1. Check Kernel Version

uname -r
# If >= 6.12, proceed to next steps

2. See If Lockdown Is Enabled

cat /sys/kernel/security/lockdown
# You should see something like "none", "integrity", or "confidentiality"

If the output is none (and you’re booted with Secure Boot), you’re exposed to CVE-2025-1272.

Suppose you have a custom kernel module named evil.ko

// evil.c: a trivial (and unsigned) kernel module
#include <linux/module.h>
#include <linux/kernel.h>
static int __init evil_init(void) {
    printk(KERN_INFO "Evil module loaded!\n");
    return ;
}
static void __exit evil_exit(void) {
    printk(KERN_INFO "Evil module unloaded!\n");
}
module_init(evil_init);
module_exit(evil_exit);
MODULE_LICENSE("GPL");

Build and load (on a vulnerable system)

make -C /lib/modules/$(uname -r)/build M=$PWD modules
sudo insmod evil.ko
dmesg | tail

On a properly locked-down and Secure Boot system, this should fail with a key/signature error, but on Fedora 6.12+ (exploitable), it succeeds.

References

- Linux Kernel Lockdown Documentation
- Fedora Bug Tracker: CVE-2025-1272 *(hypothetical for this discussion)*
- Upstream Kernel Commit for Lockdown Mode
- Secure Boot Overview

What Should Fedora Users Do?

- Upgrade: Watch Fedora advisories for a kernel/boot package update restoring lockdown-on-by-default.
- Manually enable lockdown: Boot with the lockdown=confidentiality kernel parameter, or enforce via grub:

Audit: Regularly check if lockdown is actually enabled.

Be aware: Until patched, any Secure Boot guarantees you expect under Fedora with 6.12+ are *not* effective if lockdown is off.

Conclusion

CVE-2025-1272 is a real-world Secure Boot bypass for Fedora Linux by disabling kernel lockdown mode with no warning starting in kernel 6.12. Attackers with root can load unsigned modules, access sensitive kernel internals, and break system guarantees. Fedora users running Secure Boot should check their systems and monitor for updates.

Stay safe, and keep your kernels secure!

*If you want further details or want to track the fix, follow Fedora's official advisories and the Red Hat CVE database (expected soon).*

Timeline

Published on: 02/18/2026 20:29:15 UTC
Last modified on: 02/18/2026 21:16:21 UTC