CVE-2026-99267 in Linux
Summary
by MITRE • 11/03/2026
In the Linux kernel, the following vulnerability has been resolved:
io_uring/napi: make stale entries time out after 60s
With dynamic tracking a NAPI id that hasn't been seen for a minute is meant to be dropped from the list the ring busy polls. The timeout is added to jiffies, but it is defined as 60 * SEC_CONVERSION, and SEC_CONVERSION isn't the number of jiffies in a second. It is the internal factor of __timespec64_to_jiffies(), HZ scaled up by SEC_JIFFIE_SC bits. For HZ=1000 that is 1000 << 22, which puts the timeout at about eight years. On 32-bit the multiplication overflows.
So entries are never removed, and every id that a socket of the ring ever had keeps being polled on each wait.
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Analysis
by VulDB Data Team • 11/03/2026
The Linux kernel io_uring subsystem contains a critical implementation flaw in its Network API polling mechanism regarding the handling of stale network interface identifiers. The vulnerability stems from an incorrect calculation used to determine when a NAPI ID should be considered obsolete and removed from the busy poll list. Specifically, the code attempts to add a timeout value to the current system time represented by jiffies to schedule the expiration of these entries. However, the constant used for this one-minute interval is defined as sixty multiplied by SEC_CONVERSION rather than sixty multiplied by HZ or an equivalent correct conversion factor. This error fundamentally breaks the intended logic because SEC_CONVERSION represents a scaling factor internal to timespec64 conversions and not the number of jiffies in a second.
The mathematical consequence of using this incorrect constant results in a timeout duration that is astronomically larger than the intended sixty seconds. For systems running with a standard timer frequency such as HZ equal to one thousand, the calculated value involves shifting bits by twenty-two positions after scaling, which effectively extends the timeout period to approximately eight years rather than one minute. This magnitude of error ensures that entries are never practically removed from the polling list within any reasonable operational timeframe. Furthermore on thirty-two-bit architectures this multiplication operation is prone integer overflow conditions due to the large resulting values exceeding the capacity of a signed three2-bit integer variable, which can lead to undefined behavior or negative timeout values depending on the specific implementation details and compiler optimizations involved in handling these arithmetic operations.
From an operational impact perspective this flaw leads to severe resource exhaustion and performance degradation for systems utilizing io_uring with network sockets that undergo frequent interface changes or reconfigurations. Since stale NAPI IDs are never pruned from the busy poll list every single wait operation on a ring associated with such a socket will iterate through all previously assigned identifiers regardless of their relevance. This results in unnecessary CPU cycles being consumed during polling operations and can significantly increase latency for network I/O requests. In environments where sockets frequently change interfaces or when many connections are established over time the accumulation of these stale entries creates a linear growth in processing overhead that scales with the number of socket interface changes potentially leading to denial of service conditions through excessive processor utilization even without malicious intent from external actors.
This vulnerability aligns with CWE-787 Out-of-bounds Write and CWE-190 Integer Overflow or Wraparound due to the arithmetic miscalculation causing incorrect memory access patterns in terms of logical list management rather than physical buffer overflows but it also reflects CWE-400 Uncontrolled Resource Consumption as the system fails to limit the growth of internal data structures. In terms of MITRE ATT&CK this behavior could be leveraged by an attacker aiming for resource exhaustion or denial of service particularly within cloud-native environments where io_uring is increasingly adopted for high-performance networking applications although it primarily represents a reliability issue rather than a direct privilege escalation vector unless combined with other flaws to trigger kernel panics via the overflow conditions on thirty-two-bit systems.
Mitigation strategies should focus on applying upstream kernel patches that correct the timeout calculation logic by replacing SEC_CONVERSION with the appropriate jiffies-per-second constant such as HZ or using proper time conversion helpers like msecs_to_jiffies for clarity and correctness. System administrators managing affected kernels must ensure their distributions provide updated packages containing this fix particularly those targeting thirty-two-bit architectures where integer overflow risks are higher until patching is applied. Developers integrating io_uring into applications should also implement application-level timeouts and monitoring to detect abnormal polling latencies that may indicate the presence of stale entries accumulating in the kernel space while awaiting official vendor updates for their specific operating system versions.