CVE-2022-49870 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
capabilities: fix undefined behavior in bit shift for CAP_TO_MASK
Shifting signed 32-bit value by 31 bits is undefined, so changing significant bit to unsigned. The UBSAN warning calltrace like below:
UBSAN: shift-out-of-bounds in security/commoncap.c:1252:2 left shift of 1 by 31 places cannot be represented in type 'int' Call Trace: <TASK> dump_stack_lvl+0x7d/0xa5 dump_stack+0x15/0x1b ubsan_epilogue+0xe/0x4e __ubsan_handle_shift_out_of_bounds+0x1e7/0x20c cap_task_prctl+0x561/0x6f0 security_task_prctl+0x5a/0xb0 __x64_sys_prctl+0x61/0x8f0 do_syscall_64+0x58/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd </TASK>
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Analysis
by VulDB Data Team • 11/11/2025
The vulnerability CVE-2022-49870 addresses a critical undefined behavior issue within the Linux kernel's capability handling mechanism, specifically in the CAP_TO_MASK macro implementation. This flaw resides in the security/commoncap.c file at line 1252 where a signed 32-bit integer undergoes a left shift operation by 31 bits, creating a scenario that violates fundamental programming standards and introduces potential security risks. The undefined behavior arises from the violation of the C standard's requirement that shifting a signed integer by a number of bits equal to or greater than its width results in undefined behavior, as classified under CWE-758. When the kernel's userspace interface processes capability-related system calls through the cap_task_prctl function, the undefined behavior manifests as a UBSAN (Undefined Behavior Sanitizer) warning, indicating that the left shift of the value 1 by 31 positions cannot be represented in the type 'int'.
The operational impact of this vulnerability extends beyond simple compilation warnings, as it represents a potential attack vector that could be exploited to manipulate kernel memory or bypass security controls. The specific call trace demonstrates that the issue occurs during prctl system calls which are used to manipulate process attributes including capabilities, making this flaw particularly dangerous as it could allow privilege escalation or security bypass attacks. The undefined behavior could lead to unpredictable kernel state changes, memory corruption, or execution flow manipulation that attackers could potentially leverage to gain elevated privileges or compromise system integrity. This vulnerability directly relates to the ATT&CK technique T1068 which involves exploiting vulnerabilities in privilege escalation mechanisms, and represents a classic example of how seemingly minor implementation flaws in kernel code can create significant security implications.
The fix implemented for CVE-2022-49870 involves changing the data type from signed to unsigned to ensure that the bit shift operation remains well-defined and predictable. This modification addresses the root cause by preventing the undefined behavior that occurs when shifting signed integers beyond their representable range, thereby ensuring that capability masks are properly computed and validated. The solution aligns with secure coding practices that emphasize avoiding undefined behaviors in systems programming, particularly in kernel space where such issues can have catastrophic consequences. Organizations should prioritize patching this vulnerability as it represents a foundational security issue within the Linux kernel's capability management system, and the fix demonstrates the importance of rigorous code review and static analysis in preventing subtle but critical security flaws that could be exploited by sophisticated attackers.