CVE-2020-35874 in internment Crate
Summary
by MITRE • 12/31/2020
An issue was discovered in the internment crate through 2020-05-28 for Rust. ArcIntern::drop has a race condition and resultant use-after-free.
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Analysis
by VulDB Data Team • 12/31/2020
The vulnerability identified in the internment crate for Rust represents a critical concurrency flaw that manifests through a race condition during the destruction of ArcIntern objects. This issue specifically affects the ArcIntern::drop method where multiple threads can simultaneously access and manipulate shared memory structures, creating conditions where memory deallocation occurs while references to the freed memory remain accessible. The race condition emerges from inadequate synchronization mechanisms within the reference counting implementation that governs how ArcIntern manages shared ownership of interned strings or data structures.
The technical flaw stems from the fundamental design of the ArcIntern type which relies on atomic reference counting to manage shared resources across multiple threads. When multiple threads attempt to drop or decrement references to the same ArcIntern object simultaneously, the ordering of memory operations becomes unpredictable. This creates a window where one thread may complete the decrement operation and subsequently free the underlying memory while another thread is still accessing that memory location, resulting in a use-after-free condition. The vulnerability directly relates to CWE-416 which describes the use of memory after it has been freed, and more specifically aligns with CWE-362 which addresses race conditions in concurrent programming scenarios.
The operational impact of this vulnerability extends beyond simple memory corruption as it can be exploited by malicious actors to achieve arbitrary code execution within applications that utilize the internment crate. When a use-after-free condition occurs, attackers can potentially manipulate the freed memory layout to redirect program flow or inject malicious payloads. The vulnerability affects all versions of the crate up to and including the 2020-05-28 release, making it particularly concerning for systems that have not yet updated their dependencies. Applications using ArcIntern in multi-threaded environments are most susceptible to exploitation as the race condition requires concurrent access patterns to manifest.
Mitigation strategies should focus on implementing proper synchronization mechanisms around the ArcIntern drop operations and ensuring thread-safe reference counting implementations. The recommended approach involves either upgrading to a patched version of the crate that properly handles concurrent access to shared resources or implementing application-level locks to serialize access to ArcIntern objects during destruction phases. Additionally, developers should consider using alternative crates or implementing custom internment solutions that provide better guarantees for concurrent environments. From an operational security standpoint, monitoring systems should be configured to detect unusual memory access patterns and potential exploitation attempts targeting similar race conditions. The ATT&CK framework categorizes this type of vulnerability under privilege escalation techniques where attackers leverage memory corruption flaws to gain unauthorized system access, making it essential for organizations to maintain updated dependency versions and conduct regular security assessments of their Rust applications.