CVE-2021-45947 in Wasm3
Summary
by MITRE • 01/01/2022
Wasm3 0.5.0 has an out-of-bounds write in Runtime_Release (called from EvaluateExpression and InitDataSegments).
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Analysis
by VulDB Data Team • 01/05/2022
The vulnerability CVE-2021-45947 affects Wasm3 version 0.5.0 and represents a critical out-of-bounds write condition within the runtime execution environment. This issue manifests specifically in the Runtime_Release function which is invoked during the evaluation of expressions and initialization of data segments. The flaw occurs when the runtime processes WebAssembly modules that contain malformed or malicious data structures, leading to memory corruption that can be exploited by attackers to execute arbitrary code or cause system instability. The vulnerability stems from insufficient bounds checking in memory management operations during the module lifecycle, particularly when releasing runtime resources.
The technical implementation of this vulnerability involves improper handling of memory pointers and buffer boundaries during the cleanup phase of WebAssembly module execution. When EvaluateExpression and InitDataSegments functions call Runtime_Release, the system fails to validate array indices or memory offsets against allocated buffer sizes, resulting in writes beyond the intended memory boundaries. This type of vulnerability falls under CWE-787: "Out-of-bounds Write" which is classified as a memory safety issue in the Common Weakness Enumeration catalog. The flaw essentially allows an attacker to overwrite adjacent memory locations, potentially corrupting critical runtime data structures or executing malicious payloads through controlled memory corruption.
The operational impact of CVE-2021-45947 extends beyond simple system crashes or hangs, as it represents a potential code execution vector that can be leveraged in various attack scenarios. Systems utilizing Wasm3 0.5.0 for WebAssembly module execution are at risk when processing untrusted input, making web applications, server-side environments, and embedded systems particularly vulnerable. Attackers could exploit this vulnerability through crafted WebAssembly modules that trigger the specific code path leading to the out-of-bounds write. The ATT&CK framework categorizes this as a memory corruption technique under the T1059.007 sub-technique for "Command and Scripting Interpreter: PowerShell" or more broadly as T1068: "Exploitation for Privilege Escalation" when the vulnerability leads to privilege escalation opportunities. The vulnerability affects systems where Wasm3 is used as a WebAssembly interpreter, particularly in server environments where untrusted WebAssembly code execution is permitted.
Mitigation strategies for CVE-2021-45947 primarily involve immediate upgrading to a patched version of Wasm3 where the bounds checking has been properly implemented. Organizations should also implement strict input validation and sandboxing measures when processing WebAssembly modules, ensuring that all external inputs are validated before module execution. Additionally, runtime monitoring and intrusion detection systems should be configured to detect anomalous memory access patterns that might indicate exploitation attempts. The fix should include comprehensive bounds checking in the Runtime_Release function and related memory management routines to prevent out-of-bounds writes. Security teams should also consider implementing application whitelisting policies and network segmentation to limit the potential impact of successful exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify any similar memory safety issues in other components of the WebAssembly execution stack.