AI Discovers an 18-Year-Old Linux Kernel Vulnerability Before Anyone Else

Vulnerability Overview

On 2026‑07‑23 a six‑line patch was merged into the Linux mainline to fix CVE‑2026‑64564, a use‑after‑free bug in the SCTP protocol stack that had existed since kernel 2.6.25 (2008). The bug, named SCTPhantom, allows a local user to obtain root and, when exploited from a container, to escape to the host.

Root Cause

The bug is triggered when three specific parameters appear in a single SCTP message in a particular order: an address‑deletion operation frees a kernel object, and a subsequent operation accesses the same object, creating a use‑after‑free condition. The vulnerable code resides in the SCTP ASCONF handling path and spans multiple processing stages, which explains why it evaded fuzzing and manual audits for 18 years.

Discovery Process

Corvus AI, an autonomous vulnerability‑research agent, identified the bug on 2026‑07‑12 and generated a KASAN PoC that caused a kernel crash. The agent then iteratively performed root‑cause analysis, verified control over the freed object, collected required address information, and refined the exploit under realistic kernel defenses. After several cycles the PoC was turned into a stable local‑privilege‑escalation exploit that yields root on a standard user account.

Cross‑Distribution Migration

To assess impact on other distributions, the exploit code was given to the agent for migration to Debian 13. The agent automatically compared the TencentOS and Debian kernels, relocated and adjusted 29 kernel offsets and symbols, and rebuilt the exploit based on compilation and runtime feedback. The complete migration and verification took approximately three hours, confirming the exploit works on Debian’s default kernel.

Verification Matrix

TencentOS Server – local privilege escalation (default configuration)

Debian 13 – local privilege escalation (default configuration)

Ubuntu 24.04 – local privilege escalation (default configuration)

RHEL 9.8 / Rocky Linux 9.8 – local privilege escalation (requires SCTP module loaded)

In Docker containers the vulnerability also enables container‑escape to the host.

Patch Details

The fix, merged on 2026‑07‑23, modifies six lines in sctp.c to avoid freeing the ASCONF transport during DEL‑IP processing. Commit hash: 9b2854f86f0b56e9027d68e7a3fc909d1a9b566f. The patch was back‑ported to the stable branch on 2026‑08‑03.

Additional Findings

During the same research campaign Corvus AI independently discovered a second local‑privilege‑escalation bug in the Linux Open vSwitch module (CVE‑2026‑64531, “OVSwrap”) and produced a stable root exploit.

Timeline

2026‑07‑12 – Bug discovered, KASAN PoC generated.

2026‑07‑14 – SCTP maintainer acknowledged the issue.

2026‑07‑15 to 23 – Privilege‑escalation validation on multiple distributions.

2026‑07‑23 – Fix merged into mainline (commit 9b2854f...).

2026‑07‑27 – Exploit verified for container escape.

2026‑08‑03 – Fix back‑ported to stable branch.

2026‑08‑04 – CVE‑2026‑64564 assigned; security update released for TencentOS Server.