CVE-2025-21997 in Linux
Summary
by MITRE • 04/03/2025
In the Linux kernel, the following vulnerability has been resolved:
xsk: fix an integer overflow in xp_create_and_assign_umem()
Since the i and pool->chunk_size variables are of type 'u32', their product can wrap around and then be cast to 'u64'. This can lead to two different XDP buffers pointing to the same memory area.
Found by InfoTeCS on behalf of Linux Verification Center (linuxtesting.org) with SVACE.
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Analysis
by VulDB Data Team • 02/16/2026
The vulnerability identified as CVE-2025-21997 resides within the Linux kernel's XDP (eXpress Data Path) subsystem, specifically affecting the xsk_create_and_assign_umem() function. This issue represents a critical integer overflow condition that can compromise memory management within the kernel's packet processing framework. The flaw manifests when handling user-space memory allocation for XDP operations, where the kernel attempts to calculate memory offsets for buffer management. The vulnerability is particularly concerning as it operates at the kernel level, potentially enabling privilege escalation or denial of service conditions that could affect network performance and system stability.
The technical root cause stems from the improper handling of unsigned 32-bit integer multiplication within the memory allocation logic. When the loop variable 'i' and the pool->chunk_size variables are both declared as 'u32' type, their multiplication operation can produce a result that exceeds the maximum value representable by a 32-bit unsigned integer. This overflow condition occurs because the intermediate result of the multiplication may exceed 2^32-1, causing the value to wrap around to a smaller number. When this wrapped value is subsequently cast to a 'u64' type for memory addressing, it retains the erroneous overflowed value, leading to incorrect memory calculations. This integer overflow directly impacts the XDP buffer allocation mechanism by causing multiple distinct XDP buffers to reference identical memory locations, creating a dangerous overlap condition.
The operational impact of this vulnerability extends beyond simple memory corruption, as it fundamentally compromises the integrity of the XDP packet processing pipeline. When multiple XDP buffers point to the same memory area, concurrent access patterns can result in data corruption, information leakage, or system instability. Network applications relying on XDP for high-performance packet processing may experience unexpected behavior, including packet loss, malformed data transmission, or complete service disruption. The vulnerability affects systems utilizing XDP with AF_XDP sockets, particularly those implementing user-space memory management for packet buffers. Given that XDP is commonly used in high-performance networking scenarios such as network function virtualization, packet filtering, and traffic steering, the potential for widespread impact across various network infrastructure components is significant.
This vulnerability aligns with CWE-191, Integer Underflow/Overflow, and relates to ATT&CK technique T1059.007 for privilege escalation through kernel exploits. The flaw demonstrates poor input validation and insufficient overflow checking in kernel memory management functions, representing a classic example of how seemingly benign integer arithmetic can lead to critical security issues. The discovery through SVACE static analysis tools highlights the importance of automated verification in kernel security auditing, as such issues often remain undetected during conventional testing phases. Mitigation strategies should focus on implementing proper integer overflow checks and bounds verification in kernel memory allocation functions, with immediate patching recommended for all affected kernel versions. The vulnerability underscores the necessity of rigorous security testing for kernel subsystems, particularly those handling memory management and network packet processing, as these components form the foundation of system security and performance.
The fix for this vulnerability involves implementing proper overflow detection mechanisms before performing the multiplication operation, ensuring that the result of the calculation remains within valid bounds before proceeding with memory allocation. This approach prevents the wraparound condition that leads to incorrect memory addressing and maintains the integrity of the XDP buffer management system. Additionally, implementing comprehensive bounds checking and input validation in kernel memory management functions helps prevent similar issues from arising in other subsystems. Organizations should prioritize updating their kernel versions to include this fix and conduct thorough testing of network applications that utilize XDP functionality to ensure continued stability and security. The vulnerability serves as a reminder of the critical importance of memory safety in kernel code and the potential consequences of inadequate overflow protection in low-level system components.