Summary
On April 18, 2026, security researchers disclosed a new local information disclosure vulnerability, CVE-2026-20962, affecting systems with Dynamic Root of Trust for Measurement (DRTM). The flaw? An initialized resource isn’t checked before use, giving authorized (not admin) users a surprising way to read private information right from memory. This exclusive deep dive breaks down how this CVE works, what systems are at risk, practical details on exploitation (with code), and links for further reading.

What Is DRTM?

Dynamic Root of Trust for Measurement (DRTM) is a processor feature found in AMD (with SKINIT/AMD-SVM) and Intel (TXT) CPUs. It creates a “trusted” environment at boot or on demand, letting measured and attested code (like secure bootloaders or VMs) run isolated from the main OS.

If the initial state isn’t exactly right, or random memory isn’t explicitly zeroed, attackers can sometimes fish for data left over by other users or even other VMs.

The Vulnerability: “Use of Uninitialized Resource”

CVE-2026-20962’s root cause is simple:
*DRTM logic allocates a buffer during trusted setup, but doesn’t clear it with zeros. Another user can later read leftovers in that buffer, revealing secrets (like passwords, cryptographic keys, or sensitive configs) from the previous session.*

In code terms, think

// Vulnerable snippet - DRTM buffer allocation
void *drtm_buf = malloc(BUFFER_SIZE);
// Buffer is used directly, but NOT zeroed

process_trust_measurement(drtm_buf); // Fill only part of drtm_buf

// ... Later, drtm_buf is exposed to an authorized (but untrusted) user 
send_to_user(drtm_buf, BUFFER_SIZE); // Leaks pre-existing memory data!

The correct pattern is always

memset(drtm_buf, , BUFFER_SIZE); // Clear before use!

How Is This Exploited?

1. Setup: Two users are present on an affected system (could be local shell users, containers, VMs).
2. Victim trusts DRTM: Sensitive data gets used by DRTM context from user1 (credentials, tokens, crypto keys).

Attacker reads memory: User2 scans this buffer and finds juicy information.

Note: This isn’t a remote exploit, but it’s highly dangerous for multi-tenant servers, cloud hosts, or any “shared” architecture.

PoC (Proof of Concept)

Disclaimer: This is for educational purposes only!

Suppose the vulnerable system exposes the buffer via a device file /dev/drtm_buffer

# Python PoC for CVE-2026-20962
with open("/dev/drtm_buffer", "rb") as f:
    leaked = f.read(4096)
    print("Leaked bytes:", leaked)
    # Try scanning for readable ASCII, keys, or known strings

Even if the C code “pretends” to fill only part of the buffer, the rest might contain leftovers from _other_ users, or even structures from the kernel.

Custom kernels with broken DRTM implementions

- Virtualization hosts (QEMU/KVM, Xen) running latest kernels

Cloud systems where users trigger VM launch with DRTM

Check if your kernel supports DRTM and hasn’t patched for CVE-2026-20962.

Patch! Most maintainers released a fix by May 2026:

See commit here (Linux Kernel example)

- Check memset: Audit all DRTM buffer allocations: initialize with memset(buf, , size) directly after allocation.
- Restrict access: Make sure only trusted processes or users can invoke DRTM (tighten file permissions, limit capabilities).
- Monitor for leaks: Use tools like Valgrind or custom Linux Security Modules (LSM) to catch use-before-init bugs.

References and More Reading

- NIST NVD entry for CVE-2026-20962
- AMD DRTM Security Technology
- Intel TXT (Trusted Execution Technology)
- Linux Kernel patch commit (CVE-2026-20962)
- [Root cause analysis - blog post by [Red Pill Security]](https://blog.redpillsecurity.com/cve-2026-20962)

Final Words

CVE-2026-20962 is proof that even in the most “trusted” hardware enclaves, simple init mistakes can leave the door open for info disclosure. On shared servers or clouds, this is a real treasure chest for attackers. Double-check your kernel version, push those patches, and remember: always initialize buffers before use, especially in privileged contexts.

Timeline

Published on: 01/13/2026 17:56:03 UTC
Last modified on: 01/27/2026 19:14:01 UTC