CVE-2015-7837

What it actually does

Local users bypass intended securelevel/secureboot restrictions via improper handling of the secure_boot flag across kexec reboot on UEFI Secure Boot enabled systems.

Why it matters to the business

Attackers with local access can circumvent boot-time security controls, increasing risk of unauthorized code execution or persistence on affected systems; urgency is low given no KEV listing or ransomware use but the flaw affects widely deployed Linux distributions.

How an attack unfolds

An authenticated local attacker prepares a malicious kexec payload that exploits the flag mishandling during reboot, allowing the system to boot without enforcing Secure Boot restrictions; no named threat actors are associated.

How to fix it

Apply kernel updates from distribution vendors that correctly propagate the secure_boot flag; for the listed product upgrade wordpress (Bitnami) to 5.5.2 or later.

How to confirm the fix worked

Confirm kernel version and Secure Boot status post-update; verify that kexec operations respect secure_boot flag by testing reboot behavior under UEFI.

Typical attack path

1. Obtain local user access on target system
2. Trigger kexec reboot with crafted kernel/initrd images
3. Leverage mishandled secure_boot flag to bypass restrictions
4. Execute unauthorized code or load unsigned components

How to detect it

Review system logs for kexec invocations around reboot events; look for processes or scripts that manipulate kernel images or boot flags on UEFI systems.

What your security team should do

• Prioritize patching systems booted with UEFI Secure Boot enabled
• Audit local user privileges and kexec usage
• Monitor for unusual kexec activity in system logs