CVE-2026-89605
Summary
by MITRE • 09/11/2026
In the Linux kernel, the following vulnerability has been resolved:
ecryptfs: release message context on send failure
ecryptfs_send_message_locked() moves a message context from the free list to the allocated list before sending the request to the userspace daemon.
If ecryptfs_send_miscdev() fails, the context is left on the allocated list and cannot be reused. Move it back to the free list on failure and clear the caller's pointer.
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Analysis
by VulDB Data Team • 09/11/2026
The vulnerability identified in the Linux kernel within the eCryptFS filesystem module represents a resource management flaw that can lead to memory leaks or denial of service conditions under specific error handling scenarios. The core issue resides in the ecryptfs_send_message_locked function, which is responsible for managing message contexts used for communication between the kernel space and userspace daemons involved in encryption operations. During normal operation, this function moves a message context from a free list to an allocated list before initiating transmission of the request to the associated userspace daemon. This mechanism ensures that resources are tracked correctly while active requests are pending completion or response.
The critical flaw occurs when the subsequent call to ecryptfs_send_miscdev fails due to various potential reasons such as device unavailability, buffer issues, or other I/O errors. In the original implementation, if this send operation encounters an error, the message context remains erroneously placed on the allocated list rather than being returned to the free list. Consequently, the kernel loses track of this resource because it is no longer available for reuse by subsequent operations but also cannot be properly freed or recycled since its state suggests it is still in use. Over time, repeated occurrences of such failures can exhaust the pool of available message contexts, effectively leading to a denial of service where legitimate encryption requests may fail due to lack of resources.
This type of vulnerability aligns with CWE-401, which describes missing release of memory after effective usage, and falls under the broader category of improper resource management often associated with CWE-755: Improper Handling of Unexpected or Unusual Input Conditions when considering how error paths are handled within complex subsystems. From an ATT&CK perspective, while this is not directly exploitable for remote code execution without additional conditions, it contributes to availability impact similar to techniques observed in resource exhaustion attacks where attackers might attempt to trigger repeated failures to deplete system resources gradually.
The operational impact of this flaw extends beyond simple memory leakage as it affects the stability and reliability of encrypted filesystem operations on systems relying heavily on eCryptFS for data protection at rest. Administrators managing environments with high volumes of cryptographic transactions could experience degraded performance or complete service interruption if the message context pool becomes depleted due to unhandled error conditions in the send path. This is particularly concerning in production environments where consistent availability of encryption services is critical for compliance and security postures.
Mitigation strategies primarily involve applying kernel patches that correct the logic within ecryptfs_send_message_locked to ensure proper cleanup upon failure. Specifically, developers must verify that any message context moved to the allocated list during a failed send operation is immediately returned to the free list and that references held by callers are cleared appropriately to prevent dangling pointer issues or double-free scenarios. System administrators should monitor kernel logs for signs of resource exhaustion related to eCryptFS components and ensure their systems run updated kernels containing these fixes. Regular auditing of error handling paths in critical subsystems remains essential to maintaining robust security postures against such subtle but impactful vulnerabilities.