CVE-2021-29491 in mixme
Summary
by MITRE • 05/06/2021
Mixme is a library for recursive merging of Javascript objects. In Node.js mixme v0.5.0, an attacker can add or alter properties of an object via 'proto' through the mutate() and merge() functions. The polluted attribute will be directly assigned to every object in the program. This will put the availability of the program at risk causing a potential denial of service (DoS). The problem is corrected starting with version 0.5.1; no workarounds are known to exist.
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Analysis
by VulDB Data Team • 05/12/2021
The CVE-2021-29491 vulnerability affects the mixme JavaScript library, a utility for recursive object merging in Node.js environments. This flaw resides in the mutate() and merge() functions of version 0.5.0, where improper handling of prototype pollution allows attackers to manipulate object properties through the 'proto' key. The vulnerability represents a classic prototype pollution attack vector that can be exploited to compromise application availability and stability. The issue stems from the library's failure to properly sanitize input when processing object merging operations, creating opportunities for malicious actors to inject properties into the prototype chain.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious input containing a 'proto' property within object structures passed to the mixme functions. During the recursive merging process, the library fails to validate or sanitize these prototype references, allowing the attacker to inject properties that get propagated to all objects within the program's execution context. This creates a widespread impact where every object in memory becomes vulnerable to the injected properties, fundamentally altering the program's behavior and potentially leading to unexpected execution paths. The vulnerability is classified under CWE-471 as "Modification of Externally-Controllable Resource" and aligns with ATT&CK technique T1211 for "Exploitation for Privilege Escalation" when considering the broader impact on application integrity.
The operational impact of CVE-2021-29491 extends beyond simple denial of service scenarios, as prototype pollution can lead to more severe consequences including arbitrary code execution in certain contexts. When objects are polluted through the prototype chain, it can cause cascading failures throughout the application's object model, potentially leading to crashes, data corruption, or unexpected behavior that affects system availability. The vulnerability affects all programs using mixme v0.5.0, making it particularly dangerous in environments where this library is widely deployed. The lack of known workarounds forces organizations to upgrade to version 0.5.1 or later, highlighting the critical nature of this flaw. The DoS potential arises because polluted objects can cause infinite loops during property enumeration or trigger unexpected behavior in JavaScript engines when they encounter the malicious prototype modifications, ultimately compromising the application's ability to function properly and maintain service availability.