CVE-2026-99206 in Linux
Summary
by MITRE • 10/28/2026
In the Linux kernel, the following vulnerability has been resolved:
scsi: target: iscsi: Fix race in discovery auth updates
Separate configfs opens can concurrently update the discovery AuthMethod parameter. Both callers may free the same value in iscsi_update_param_value(), causing a double-free.
Protect the lookup and replacement with the discovery TPG access lock, as used by the other TPG configfs parameter updates.
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Analysis
by VulDB Data Team • 10/28/2026
The Linux kernel contains a concurrency vulnerability within the SCSI target iSCSI implementation that arises from improper synchronization during configuration file system operations. Specifically, the race condition occurs in the handling of discovery authentication parameters when multiple concurrent accesses to the configfs interface attempt to update the AuthMethod parameter for discovery targets. This scenario involves separate threads or processes opening and modifying the same configuration object simultaneously without adequate mutual exclusion mechanisms protecting the critical section where the parameter value is looked up and replaced.
The technical flaw centers on a double-free memory corruption issue triggered by concurrent execution paths in the iscsi_update_param_value function. When two distinct configfs open operations proceed concurrently, both may retrieve pointers to the same existing authentication method string or structure. As each thread proceeds to update the parameter, it attempts to free the previously held value associated with that configuration node. Because there was no locking mechanism preventing simultaneous access to this specific resource, both threads independently execute the deallocation routine on the identical memory address. This results in a double-free condition, which corrupts the kernel heap metadata and can lead to system instability or potential exploitation for arbitrary code execution depending on how the freed memory is subsequently allocated and used by other subsystems.
From an operational impact perspective, this vulnerability poses significant risks to systems relying on Linux SCSI target functionality, particularly those operating as iSCSI storage servers in enterprise environments. The immediate consequence of triggering this race condition is a kernel panic or crash due to heap corruption, leading to service denial for connected initiators attempting to access shared storage resources. Beyond availability issues, the double-free vulnerability represents a serious security risk that could potentially be leveraged by an attacker with local access to manipulate memory structures within the kernel space. Such manipulation might allow privilege escalation from unprivileged user contexts to root-level control over the host system, compromising data integrity and confidentiality of stored information managed through the iSCSI target interface.
To mitigate this vulnerability, developers have implemented a fix that introduces proper synchronization primitives into the affected code path. The solution involves protecting both the lookup and replacement operations within iscsi_update_param_value with the discovery Target Portal Group access lock. This approach aligns the handling of discovery authentication updates with existing practices used for other TPG configfs parameter modifications, ensuring consistent locking behavior across similar configuration changes. By serializing access to these critical sections using the appropriate mutex or spinlock associated with the target portal group, concurrent threads are forced to wait their turn rather than executing conflicting operations simultaneously. This eliminates the window of opportunity where both processes could hold references to the same memory block and subsequently attempt independent deallocation.
This vulnerability is classified under CWE-415 Double Free, which describes situations where a program frees an object twice without resetting the pointer or ensuring that subsequent free calls are safe from re-execution on already freed memory. In terms of attack vector classification within MITRE ATT&CK frameworks, this issue relates to techniques involving resource management errors and potentially privilege escalation through kernel exploitation if successfully triggered by local users with sufficient permissions to modify iSCSI target configurations. The fix emphasizes the importance of maintaining consistent locking strategies across all configuration interfaces in complex subsystems like SCSI targets to prevent subtle concurrency bugs that manifest only under specific timing conditions difficult to reproduce during standard testing phases.