CVE-2024-50102

What it actually does

The flaw permits speculative execution of non-canonical kernel memory accesses on AMD Zen 5 processors, allowing leakage of kernel data through gadgets that use the result of user/kernel address checks even when STAC/CLAC serialization is employed.

Why it matters to the business

Attackers could extract sensitive kernel memory contents on affected systems, increasing risk of credential or data theft; the issue affects many Linux distributions and downstream dependents but has low exploitation likelihood so far with no ransomware use reported.

How an attack unfolds

An attacker with local code execution crafts a speculation gadget that performs a non-canonical access, relies on the renamed AC bit on Zen 5 to keep the speculation window open, and uses the leaked kernel data in a side-channel to read privileged memory; listed threat actors have conducted similar kernel speculation campaigns but none are confirmed exploiting this specific issue.

How to fix it

Upgrade the Linux kernel to a version containing the STAC/CLAC pairing fix for address masking and valid_user_address checks; for the listed flashplugin-nonfree package on Ubuntu 14.04 LTS apply version 11.2.202.521ubuntu0.14.04.1 or later.

How to confirm the fix worked

Confirm kernel version after update contains the address masking speculation fix; test that user-space probes no longer leak speculative data on Zen 5 hardware; verify package version matches the fixed flashplugin-nonfree release where applicable.

Typical attack path

1. Obtain local unprivileged execution on target system
2. Locate or construct a kernel gadget using address masking or access_ok results
3. Trigger non-canonical speculation via crafted user-space address
4. Observe side-channel leakage of speculative kernel data
5. Reconstruct sensitive kernel memory contents

How to detect it

Review kernel logs and audit records for unusual speculation-related activity or failed address checks; correlate with any listed threat actor tooling that targets kernel uninitialized or out-of-bounds reads, though no specific post-exploitation artifacts are known.

What your security team should do

• Prioritize kernel updates on all AMD Zen 5 systems within standard patch windows given low EPSS and no KEV status
• Monitor for any new exploit maturity or threat actor campaigns targeting this speculation class
• Apply the exact fixed package versions provided for flashplugin-nonfree on Ubuntu 14.04 LTS