CVE-2025-40267 in Linux
Summary
by MITRE • 12/07/2025
In the Linux kernel, the following vulnerability has been resolved:
io_uring/rw: ensure allocated iovec gets cleared for early failure
A previous commit reused the recyling infrastructure for early cleanup, but this is not enough for the case where our internal caches have overflowed. If this happens, then the allocated iovec can get leaked if the request is also aborted early.
Reinstate the previous forced free of the iovec for that situation.
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Analysis
by VulDB Data Team • 02/23/2026
The vulnerability identified as CVE-2025-40267 resides within the Linux kernel's io_uring subsystem, specifically affecting the read/write operations handling mechanism. This issue manifests in the io_uring runtime environment where asynchronous I/O operations are processed through a sophisticated infrastructure designed to optimize performance and resource management. The io_uring subsystem represents a critical component in modern Linux systems, enabling high-performance asynchronous I/O operations that are fundamental to database servers, web servers, and other high-throughput applications. The vulnerability stems from improper memory management during error handling scenarios, particularly when early request failures occur during I/O processing.
The technical flaw involves a regression in the io_uring subsystem's memory management strategy where the recycling infrastructure for iovec (input/output vector) structures was modified to handle early cleanup scenarios. However, this modification fails to account for situations where internal caches have overflowed, creating a scenario where allocated iovec structures can become permanently leaked. The iovec structures are essential for describing scatter-gather I/O operations, allowing data to be read from or written to multiple non-contiguous memory regions. When the internal caching mechanism exceeds its capacity, the system cannot properly release these iovec allocations, leading to memory leaks that accumulate over time. This issue represents a classic memory management regression where optimization efforts for normal operation inadvertently create failure conditions that were previously handled correctly.
The operational impact of this vulnerability extends beyond simple memory consumption issues, potentially leading to system instability and performance degradation in high-load environments. When iovec structures leak due to early request aborts during cache overflow conditions, the cumulative effect can result in significant memory pressure that may eventually cause system resource exhaustion. Applications relying heavily on io_uring for asynchronous operations, such as database engines, storage systems, and network services, could experience degraded performance or even system crashes as memory resources become increasingly constrained. The vulnerability affects systems where io_uring is extensively used, particularly in server environments where sustained high I/O operations are common. The issue is particularly concerning because it operates silently in the background, with memory leaks accumulating gradually until they reach critical thresholds that impact system stability and availability.
Mitigation strategies should focus on immediate kernel updates to address the specific regression in io_uring's memory management. System administrators should prioritize applying the patched kernel version that reinstates the forced free mechanism for iovec structures during cache overflow scenarios. Additionally, monitoring systems should be enhanced to track memory usage patterns and detect potential memory leak accumulation in applications utilizing io_uring. The fix addresses the root cause by restoring the previous behavior that ensured iovec structures are properly freed regardless of cache overflow conditions, aligning with best practices for memory management in high-performance I/O subsystems. This vulnerability demonstrates the importance of thorough testing during optimization efforts, particularly in critical kernel subsystems where memory management failures can have cascading effects on system stability and performance. The issue aligns with CWE-401: Improper Release of Memory and relates to ATT&CK technique T1490: Inhibit System Recovery, as the memory leaks can eventually lead to system instability and resource exhaustion that impacts system recovery capabilities.