CVE-2026-71227 in Red Hat
Summary
by MITRE • 08/05/2026
A flaw was found in libkcapi. A local attacker can influence an application that uses the Asynchronous Input/Output (AIO) interface. By reusing an AIO-enabled handle after a prior completion error, the _kcapi_aio_read_all() function can enter a non-terminating wait loop. This can lead to a persistent denial of service, making the affected application or thread unresponsive.
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Analysis
by VulDB Data Team • 08/05/2026
The vulnerability in libkcapi represents a critical race condition and resource management flaw that fundamentally undermines the reliability of asynchronous I/O operations within kernel cryptographic API implementations. This issue specifically affects applications leveraging the Asynchronous Input/Output interface where proper error handling and state management become paramount for system stability. The flaw manifests when a local attacker manipulates the sequence of operations by reusing an AIO-enabled handle that has already encountered a prior completion error, creating a dangerous state transition that compromises the application's operational integrity.
The technical execution of this vulnerability relies on the improper handling of asynchronous I/O contexts within the _kcapi_aio_read_all() function implementation. When an AIO handle experiences a completion error during a previous operation, the system should properly terminate or reset the context before allowing reuse. However, the current implementation fails to validate the handle's state adequately, leading to a scenario where subsequent operations on the same handle can result in indefinite blocking within an internal wait loop. This behavior constitutes a classic denial of service condition where the application thread becomes perpetually suspended, unable to process additional requests or respond to system events.
The operational impact extends beyond simple service disruption to encompass potential system-wide stability concerns, particularly in environments where multiple cryptographic operations occur concurrently. Applications utilizing libkcapi for kernel-level encryption, decryption, or hashing operations become vulnerable to persistent hang conditions that can propagate through system call chains and affect other dependent services. The vulnerability's local nature means it requires physical access or process-level privileges to exploit, but the consequences remain severe given that a single malicious operation can effectively瘫痪 an entire application thread or process. This aligns with CWE-362, which addresses concurrent execution issues related to race conditions in resource management and synchronization.
From an attack perspective, this vulnerability demonstrates how seemingly minor state management oversights can create significant security implications within cryptographic libraries that form the foundation of system security infrastructure. The ATT&CK framework categorizes this as a denial of service technique under the T1499 sub-technique, specifically targeting application availability through resource exhaustion or blocking conditions. The flaw's exploitation requires minimal privileges and can be automated, making it particularly dangerous in multi-user environments where malicious users might leverage this weakness to disrupt system services without requiring elevated access rights.
Mitigation strategies must focus on comprehensive state validation within the AIO handling code path, implementing proper error recovery mechanisms that prevent handle reuse in error states. The recommended approach includes adding explicit checks for completion status before allowing handle reuse, implementing timeout mechanisms for wait loops, and ensuring proper cleanup procedures that reset I/O contexts upon error conditions. Additionally, applications should implement robust monitoring and recovery protocols that can detect and terminate stuck threads to prevent cascading failures throughout the system architecture. Organizations should prioritize patching affected versions of libkcapi and consider implementing application-level safeguards that isolate potentially vulnerable cryptographic operations within separate process boundaries to contain any potential impact from exploitation attempts.