CVE-2021-33631

What it actually does

Integer overflow in openEuler Linux kernel filesystem modules causes memory corruption allowing forced wraparound that can lead to arbitrary code execution or kernel panic with local privileges.

Why it matters to the business

Local attackers on affected systems can escalate privileges, read or modify sensitive data, or crash servers, increasing risk of data breaches and operational downtime on Linux-based infrastructure.

How an attack unfolds

An attacker with local low-privileged access crafts malicious filesystem operations or inputs that trigger the integer overflow in the kernel's filesystem handling code, resulting in memory corruption that is leveraged for privilege escalation or denial of service.

How to fix it

Upgrade openEuler kernel to 4.19.90-2401.3 or newer, or 5.10.0-183.0.0 or newer; apply the upstream Linux kernel fix at commit 5c099c4fdc438014d5893629e70a8ba934433ee8 and rebuild or patch affected distributions.

How to confirm the fix worked

Verify running kernel version is at or above the fixed releases; inspect source or changelog for presence of the referenced commit; test filesystem module behavior with crafted inputs in a lab environment.

Typical attack path

1. Gain local shell access on target system
2. Prepare input or filesystem image that triggers integer wraparound in affected modules
3. Execute operation causing the overflow to corrupt kernel memory
4. Chain corruption to achieve code execution or kernel control

How to detect it

Review kernel logs and audit records for unusual filesystem module crashes or errors around the time of suspicious local activity; correlate with process execution from untrusted local users.

What your security team should do

• Prioritize patching production Linux systems running vulnerable openEuler kernels within 30 days given local attack vector
• Restrict local user access and filesystem mounting privileges on unpatched hosts
• Monitor EPSS and threat actor activity for any increase in exploitation likelihood
• Include kernel version checks in regular vulnerability scanning and asset inventory