CVE-2022-49264 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
exec: Force single empty string when argv is empty
Quoting[1] Ariadne Conill:
"In several other operating systems, it is a hard requirement that the second argument to execve(2) be the name of a program, thus prohibiting a scenario where argc < 1. POSIX 2017 also recommends this behaviour, but it is not an explicit requirement[2]:
The argument arg0 should point to a filename string that is associated with the process being started by one of the exec functions. ... Interestingly, Michael Kerrisk opened an issue about this in 2008[3],
but there was no consensus to support fixing this issue then. Hopefully now that CVE-2021-4034 shows practical exploitative use[4]
of this bug in a shellcode, we can reconsider.
This issue is being tracked in the KSPP issue tracker[5]."
While the initial code searches[6][7] turned up what appeared to be
mostly corner case tests, trying to that just reject argv == NULL (or an immediately terminated pointer list) quickly started tripping[8]
existing userspace programs.
The next best approach is forcing a single empty string into argv and adjusting argc to match. The number of programs depending on argc == 0 seems a smaller set than those calling execve with a NULL argv.
Account for the additional stack space in bprm_stack_limits(). Inject an empty string when argc == 0 (and set argc = 1). Warn about the case so userspace has some notice about the change:
process './argc0' launched './argc0' with NULL argv: empty string added
Additionally WARN() and reject NULL argv usage for kernel threads.
[1] https://lore.kernel.org/lkml/[email protected]/
[2] https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html
[3] https://bugzilla.kernel.org/show_bug.cgi?id=8408
[4] https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt
[5] https://github.com/KSPP/linux/issues/176
[6] https://codesearch.debian.net/search?q=execve%5C+*%5C%28%5B%5E%2C%5D%2B%2C+*NULL&literal=0
[7] https://codesearch.debian.net/search?q=execlp%3F%5Cs*%5C%28%5B%5E%2C%5D%2B%2C%5Cs*NULL&literal=0
[8] https://lore.kernel.org/lkml/20220131144352.GE16385@xsang-OptiPlex-9020/
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Analysis
by VulDB Data Team • 10/21/2025
The vulnerability identified as CVE-2022-49264 represents a critical security flaw in the Linux kernel's execve system call implementation that emerged from longstanding ambiguities in POSIX compliance and practical exploitation patterns. This issue specifically addresses the handling of empty argument vectors when executing programs through the execve family of system calls, where the argv parameter could legitimately be passed as NULL or contain zero arguments. The vulnerability stems from the kernel's failure to properly validate and normalize argument vectors during program execution, creating potential attack vectors that could be exploited by malicious actors to bypass security controls or manipulate program execution flows.
The technical implementation of this vulnerability involves the kernel's execve function not properly handling cases where argc equals zero, which can occur when programs are invoked with empty argument lists. The Linux kernel's implementation had historically allowed such scenarios without proper enforcement of POSIX standards, where the second argument to execve should point to a filename string associated with the process being started. This inconsistency created a security gap that could be leveraged by attackers to craft exploits that manipulate the execution environment, particularly in contexts where argument validation was expected to occur. The flaw directly relates to CWE-119, which encompasses memory access errors and improper handling of buffer boundaries, and can be categorized under the broader ATT&CK technique of privilege escalation through process manipulation.
The operational impact of CVE-2022-49264 extends beyond simple compliance issues, as it directly affects the kernel's ability to maintain consistent security boundaries during process execution. When programs are launched with empty argument vectors, the kernel's handling of such cases could lead to unexpected behavior in privilege escalation scenarios, particularly when combined with other vulnerabilities like CVE-2021-4034, commonly known as PwnKit, which demonstrated how argument vector manipulation could be exploited in real-world attacks. The fix implemented by the Linux kernel developers forces a single empty string into argv when argc equals zero, adjusting the argument count accordingly and injecting this empty string into the stack space allocated by bprm_stack_limits(). This normalization approach ensures that all execve operations maintain consistent argument structures while preserving backward compatibility for legitimate use cases that might depend on the previous behavior.
Security implications of this vulnerability are significant, particularly in environments where strict security controls are enforced and process execution must be predictable and secure. The kernel's approach of issuing WARN() messages when NULL argv usage is detected provides administrators with visibility into potential issues while maintaining operational stability. The fix specifically addresses kernel threads by rejecting NULL argv usage, preventing potential exploitation vectors that could arise from improper handling of kernel-space execution contexts. This vulnerability highlights the importance of strict adherence to POSIX standards in kernel implementations and demonstrates how seemingly minor compliance issues can have substantial security implications. The solution implemented through the Linux kernel's security patching process represents a balance between maintaining backward compatibility and enforcing security best practices, ensuring that all execve operations follow standardized argument handling patterns while providing clear warnings to userspace programs that may be affected by this change.
The resolution of CVE-2022-49264 through the Linux kernel's response demonstrates the importance of continuous security auditing and the evolution of security practices in response to real-world exploitation patterns. The vulnerability's identification and subsequent patching process aligns with established security methodologies that require addressing both theoretical and practical security gaps, particularly when exploitation examples become publicly available. This case study illustrates how security researchers and kernel developers work together to identify and resolve issues that may not have been immediately apparent but can become critical threats when exploited in combination with other vulnerabilities. The implementation of the fix through proper argument vector normalization and stack space management ensures that the Linux kernel maintains its security posture while continuing to support legitimate system operations and user expectations.