PoC Released for Linux Kernel Vulnerability Allowing Privilege Escalation

A security vulnerability, tracked as CVE-2024-53141, has recently come to light in the Linux kernel’s ipset component.

This flaw enables out-of-bounds (OOB) write on the kernel heap, which threat actors can exploit to execute arbitrary code with elevated privileges.

Security researchers have now released a proof-of-concept (PoC) exploit, escalating concerns about possible real-world attacks on unpatched systems.

IP sets are an integral framework within the Linux kernel, allowing for rapid storage and matching of IP addresses and related data types, which is crucial for various firewall and network filtering tasks.

Amongst its features is the bitmap:ip set type, which uses memory-efficient bitmaps to handle large numbers of IP addresses expeditiously.

CVE-2024-53141 specifically resides in the bitmap_ip_uadt function in the ip_set_bitmap_ip.c source file.

The flaw stems from incomplete bounds checking when the IPSET_ATTR_CIDR attribute is used without the IPSET_ATTR_IP_TO parameter.

Under these circumstances, the code calculates a range of IP addresses based on the provided CIDR, but fails to ensure that the resulting start IP (ip) remains within the valid boundaries set by map->first_ip and map->last_ip.

Vulnerable Code Snippet

else if (tb[IPSET_ATTR_CIDR]) {
    u8 cidr = nla_get_u8(tb[IPSET_ATTR_CIDR]);
    ...
    ip_set_mask_from_to(ip, ip_to, cidr); // Issue arises here
}
...
if (ip_to > map->last_ip) // [Boundary check happens after the fact]
    return -IPSET_ERR_BITMAP_RANGE;
...
for (; !before(ip_to, ip); ip += map->hosts) { // Can iterate outside of allowed range
    e.id = ip_to_id(map, ip);
    ret = adtfn(set, &e, &ext, &ext, flags);
}

This logic oversight allows malicious actors to craft inputs that cause the kernel to write outside the allocated memory segment, leading to a heap overflow.

Exploit Details and Impact

In practice, an attacker can leverage this OOB write to corrupt kernel memory structures. The released PoC illustrates a multi-step attack, including:

• Leaking kernel heap addresses via manipulation of the comment feature in ipsets, which can spill sensitive information into accessible memory.
• Arbitrary memory write by abusing ipset counters, paving the path toward further exploitation.
• Heap spraying and use-after-free scenarios by manipulating internal kernel objects such as pipe_buffer, msg_msgseg, and socket buffers.
• Control of instruction pointer (RIP) to execute attacker-supplied code, ultimately allowing for privilege escalation.

The exploit culminates in overwriting the core_pattern kernel parameter, using a ROP (Return-Oriented Programming) chain to execute a user-provided binary with root privileges whenever a process crashes.

Linux users and administrators are urged to update their systems immediately.

The vulnerability affects kernels with vulnerable ipset implementations, and the presence of a public PoC significantly raises the risks of mass exploitation.

Patching or applying available mitigations is paramount to securing affected systems.

With the release of the PoC, CVE-2024-53141 is now a high-priority issue for all organizations relying on Linux systems for critical workloads.

Security teams should act swiftly to remediate the threat and monitor for any signs of exploitation in the wild.

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