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How the mentioned CVE works:
The CVE-2021-33909 vulnerability, also known as “Sequoia,” exists in the Linux kernel’s filesystem layer. The flaw is a use-after-free in the `seq_file` interface. A local attacker can trigger a race condition by invoking the `open()` and `read()` syscalls concurrently on a specific file in /proc/self. This concurrent access can cause the kernel to release a `seq_file` buffer while it is still being read. The freed memory is then reused by the kernel for other purposes. By carefully controlling this memory reuse, an attacker can leak sensitive kernel memory addresses, bypassing security protections like KASLR. This information leak is a crucial first step, which can be chained with other exploits to achieve full privilege escalation, granting root-level control over the affected system.
Platform: Linux Kernel
Version: Prior to 5.13.4
Vulnerability: Use-After-Free
Severity: Critical
date: 2021-07-20
Prediction: Patch Available
What Undercode Say:
`cat /proc/self/mountinfo`
`cat /proc/self/task//mountinfo`
`dmesg | grep “kernel pointer leak”`
`uname -r`
` Check for kernel version 5.13.4 or later`
How Exploit:
1. Leak Kernel Pointers
2. Bypass KASLR
3. Execute Privilege Escalation
4. Gain Root Access
Protection from this CVE
Update Kernel Version
Apply Vendor Patches
Restrict User Access
Impact:
Information Disclosure
Privilege Escalation
System Compromise
🎯Let’s Practice Exploiting & Learn Patching For Free:
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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