PoC Exploit Releases for CVE-2023-52447: A Linux Kernel Flaw Enabling Container Escape

The attack on CVE-2023-52447 begins with the exploitation of a use-after-free vulnerability in the Linux kernel's BPF subsystem, which is leveraged to orchestrate a race condition between two threads. This allows the attacker to modify kernel data structures, such as 'core_pattern', to achieve container escape. BlueRock's Core Pattern String Protection effectively mitigates this step by safeguarding the 'core_pattern' data structure from unauthorized modifications, thereby preventing the attacker from altering it to escape the container environment. This mechanism ensures that even if the vulnerability is exploited, the critical kernel data structures remain protected, maintaining the integrity of the container isolation.

• T1068: Exploitation for Privilege Escalation: The article describes a use-after-free vulnerability in the Linux kernel’s BPF subsystem, which can be exploited by orchestrating a race condition between two threads. This falls under the category of 'Exploitation for Privilege Escalation' as the attacker leverages the vulnerability to escape container isolation.
• T1190: Exploit Public-Facing Application: The article mentions that the PoC exploit is available on GitHub, which implies that the attackers could potentially use publicly available exploit code to achieve their objectives. This aligns with 'Exploit Public-Facing Application' where the attacker uses an existing exploit.
• T1611: Escape to Host: The vulnerability allows an attacker to modify kernel data structures, such as 'core_pattern', to achieve container escape. This involves manipulating the underlying system to gain higher privileges or escape restricted environments, which fits 'Escape to Host' technique.

F1: Exploitation of CVE-2023-52447 (Linux Kernel BPF Use-After-Free) using a Proof-of-Concept (PoC) approach targeting core_pattern for container escape.

• Attacker identifies a target system running a vulnerable Linux kernel version (v5.8 to v6.6). (Cited from: "affects Linux kernel versions from v5.8 to v6.6")
• Attacker obtains or develops a BPF program designed to trigger the use-after-free vulnerability related to arraymap pointers in arrayofmaps. (Cited from: "use-after-free flaw in the Linux kernel’s BPF subsystem, specifically related to how arraymap pointers are managed in BPF programs", "The issue occurs when a BPF program holds an arraymap pointer from an arrayofmaps without properly increasing the reference count.")
• The BPF program includes a time-consuming operation to create a window for a race condition. (Cited from: "If the BPF program performs a time-consuming operation, it can allow another thread to free the arraymap and reclaim the memory, leading to a use-after-free condition.")
• Attacker orchestrates a race condition between two threads using the crafted BPF program to trigger the use-after-free. (Cited from: "The vulnerability can be exploited by carefully orchestrating a race condition between two threads")
• Within the exploit process, the attacker manipulates a victim arraymap's max_entries and index_mask. (Cited from: "Modified victim arraymap’s maxentries and indexmask.")
• The attacker leverages the compromised victim arraymap to modify a nearby arrayofmaps entry (index 0) to point to a calculated address related to core_pattern (corepattern - structbpfarrayoffset). (Cited from: "Use victim arraymap to modified near arrayofmaps’s value index 0 arraymap as (corepattern-structbpfarrayoffset).")
• The attacker updates the arrayofmaps structure, effectively using the manipulated pointers to overwrite the system's core_pattern setting in kernel memory. (Cited from: "Update arrayofmaps to modify core_pattern.")
  • BR-42: Core Pattern String Protection - This mechanism is applicable because it specifically prevents malicious attempts to modify the core_pattern kernel string. It detects and blocks unauthorized modifications to this string, which is exactly what the attacker is attempting in this step to set up code execution upon a crash.
  • BR-39: Integrity Patch Violation - This mechanism is applicable because it detects and responds to unauthorized or malicious patch attempts within the guest kernel, including direct memory modifications like overwriting core_pattern. It would log or block this modification attempt based on policy.
  • BR-35: Kernel Integrity Protection - This mechanism is potentially applicable if the core_pattern variable resides within a kernel memory region protected by UltraSecurity™ (e.g., read-only data sections, though core_pattern is typically writable via procfs). It monitors and blocks unauthorized write attempts to protected kernel regions. However, BR-42 is more specific to core_pattern.
• By controlling core_pattern, the attacker sets up a scenario where a subsequent process crash will execute attacker-controlled code on the host, achieving container escape. (Cited from: "Achieve container escape.")