CVE-2016-4470

What it actually does

The key_reject_and_link function in security/keys/key.c fails to initialize a data structure, allowing a crafted keyctl request2 command to trigger a kernel crash via uninitialized memory access.

Why it matters to the business

Local denial-of-service crashes can interrupt services on affected systems; with over 3755 days since disclosure and stable low EPSS, immediate widespread operational risk remains low but unpatched imagemagick/imagemagick GIT instances stay exposed to local abuse.

How an attack unfolds

An attacker with local access issues a specially crafted keyctl request2 command that reaches the uninitialized data path in key_reject_and_link, resulting in a kernel panic; listed threat actors such as Linux Kernel Race Condition Vulnerability campaigns illustrate similar local kernel abuse patterns.

How to fix it

Upgrade imagemagick/imagemagick (GIT) to commit d9ccd8227c4c88a907cda5278408b73552cb0c07 or later; apply the upstream kernel patch for key.c if running affected Linux versions through 4.6.3.

How to confirm the fix worked

Confirm the running kernel or imagemagick GIT revision contains the fix commit d9ccd8227c4c88a907cda5278408b73552cb0c07; test with a non-privileged keyctl request2 that previously triggered the crash path.

Typical attack path

1. Obtain local shell or user access on target
2. Craft and execute keyctl request2 command with malicious parameters
3. Trigger uninitialized structure dereference in key_reject_and_link
4. Cause kernel panic and system crash

How to detect it

Review system logs and audit trails for keyctl invocations around crash timestamps; search kernel logs for oops or panic entries involving key_reject_and_link or keyctl request2; correlate with listed threat actor TTPs for Linux kernel key handling abuse.

• key_reject_and_link
• keyctl request2
• uninitialized data structure keyctl

What your security team should do

• Prioritize patching imagemagick/imagemagick GIT instances to d9ccd8227c4c88a907cda5278408b73552cb0c07
• Restrict local keyctl privileges via LSM or seccomp where possible
• Monitor for unexpected kernel oops or panics referencing key_reject_and_link