CVE-2026-23259 in Linux
Summary
by MITRE • 03/18/2026
In the Linux kernel, the following vulnerability has been resolved:
io_uring/rw: free potentially allocated iovec on cache put failure
If a read/write request goes through io_req_rw_cleanup() and has an allocated iovec attached and fails to put to the rw_cache, then it may end up with an unaccounted iovec pointer. Have io_rw_recycle() return whether it recycled the request or not, and use that to gauge whether to free a potential iovec or not.
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Analysis
by VulDB Data Team • 06/01/2026
The vulnerability identified as CVE-2026-23259 resides within the Linux kernel's io_uring subsystem, specifically affecting the read/write operations handling mechanism. This issue manifests in the io_req_rw_cleanup function where the kernel fails to properly manage memory resources when processing asynchronous I/O requests. The io_uring framework serves as a high-performance asynchronous I/O interface that allows applications to submit and complete I/O operations without blocking, making it critical for modern Linux systems handling substantial I/O workloads. The vulnerability stems from improper resource management during the cleanup phase of I/O operations, creating potential memory leak scenarios that could impact system stability and resource utilization.
The technical flaw occurs when an I/O request undergoes the io_req_rw_cleanup() function and possesses an allocated iovec structure that was dynamically allocated during the request processing. When this cleanup function encounters a failure during the put operation to the rw_cache, the allocated iovec pointer becomes orphaned and unaccounted for within the kernel's memory management system. This represents a classic memory leak scenario where allocated resources are not properly released back to the system, leading to gradual resource exhaustion over time. The issue is particularly concerning because it affects the kernel's internal cache management system, which is designed to optimize performance by reusing allocated structures rather than constantly allocating and deallocating memory.
The operational impact of this vulnerability extends beyond simple memory consumption issues, potentially affecting system performance and stability under heavy I/O load conditions. When the io_rw_recycle() function fails to properly recycle requests due to cache put failures, the kernel may continue to hold references to allocated iovec structures, causing gradual memory fragmentation and resource depletion. This could lead to system slowdowns, application crashes, or in severe cases, complete system instability when memory resources become exhausted. The vulnerability particularly affects systems heavily reliant on io_uring for asynchronous I/O operations, such as database servers, web servers, and high-performance computing applications that depend on efficient I/O handling.
The mitigation strategy involves modifying the io_rw_recycle() function to properly return status information indicating whether the request was successfully recycled or not. This status information must be carefully evaluated during cleanup operations to determine whether to free the potentially allocated iovec structure or retain it for proper management. The fix ensures that when cache put operations fail, the system can properly identify and free any orphaned iovec pointers, preventing memory leaks. This approach aligns with established security practices for kernel memory management and follows the principle of least privilege in resource handling. The solution addresses the root cause by implementing proper error handling and resource accounting mechanisms that prevent unaccounted memory allocations from persisting in the kernel's memory space. This vulnerability classification aligns with CWE-401, which addresses improper handling of memory allocation failures, and could potentially be leveraged by attackers to exhaust system resources through carefully crafted I/O operations, making it a significant concern for system administrators and security professionals managing Linux-based systems.