Source: cve@mitre.org
An issue was discovered in the simple-slab crate before 0.3.3 for Rust. remove() has an off-by-one error, causing memory leakage and a drop of uninitialized memory.
CVE-2020-35893 exposes a memory management flaw in the simple-slab Rust crate, leading to memory leaks and the potential for reading uninitialized memory. This can be exploited to cause a denial-of-service (DoS) or, in some scenarios, potentially leak sensitive information, impacting the availability and integrity of systems using the vulnerable crate.
Step 1: Initialization: The vulnerable simple-slab crate is initialized and used to allocate memory blocks (slabs).
Step 2: Allocation: Data is written to the allocated slabs.
Step 3: Triggering the Vulnerability: The remove() function is called to deallocate a slab. Due to the off-by-one error, the function incorrectly calculates the memory region to be freed.
Step 4: Memory Leak: The incorrect calculation results in some memory not being deallocated, leading to a memory leak. The leaked memory remains allocated but is no longer accessible through the slab's interface.
Step 5: Drop of Uninitialized Memory (Potential): In some scenarios, the incorrect calculation might lead to the remove() function attempting to drop uninitialized memory, potentially leading to a crash or information disclosure.
The vulnerability stems from an off-by-one error within the remove() function of the simple-slab crate. This error occurs when calculating the index of an element to be removed from a slab. Specifically, the calculation used to determine the end of the memory region to be freed is incorrect, leading to a failure to properly deallocate memory and, in some cases, attempting to drop uninitialized memory. This can lead to a memory leak, where allocated memory is never returned to the system, eventually leading to exhaustion of available memory. Furthermore, dropping uninitialized memory can lead to undefined behavior, potentially allowing an attacker to read sensitive information or trigger a crash. The root cause is a flawed index calculation within the remove() function, which fails to correctly account for the size of the slab or the position of the element being removed.
There is no specific evidence linking this vulnerability to known APT groups or malware campaigns. However, any memory corruption vulnerability can be exploited by sophisticated attackers. CISA KEV status is unlikely due to the nature of the vulnerability and the fact that it is in a Rust crate, which is not as commonly used in critical infrastructure as other languages. However, the potential for DoS makes it a risk.
Monitor system memory usage for unusual growth patterns, which could indicate a memory leak.
Analyze crash dumps or core files for signs of memory corruption or attempts to access uninitialized memory.
Implement fuzzing and static analysis on code that uses the simple-slab crate to identify potential memory management issues.
Network monitoring for unusual traffic patterns that might indicate an attempt to exploit a DoS vulnerability. This is less effective, but can be used in conjunction with other methods.
Use memory profiling tools (e.g., Valgrind for Rust) to identify memory leaks and other memory management errors.
Upgrade the simple-slab crate to version 0.3.3 or later.
Review and audit all code that uses the simple-slab crate to ensure that the vulnerability is not being exploited.
Implement robust memory management practices, including the use of memory sanitizers and fuzzing, to prevent future memory corruption vulnerabilities.
Regularly update all dependencies to the latest versions to address known vulnerabilities.
Implement defense-in-depth strategies, such as limiting the resources available to applications and using intrusion detection systems (IDS) to detect malicious activity.