CVE-2020-28491 in WebLogic Server
Summary
by MITRE • 02/18/2021
This affects the package com.fasterxml.jackson.dataformat:jackson-dataformat-cbor from 0 and before 2.11.4, from 2.12.0-rc1 and before 2.12.1. Unchecked allocation of byte buffer can cause a java.lang.OutOfMemoryError exception.
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Analysis
by VulDB Data Team • 08/13/2022
The vulnerability CVE-2020-28491 represents a critical memory allocation issue within the Jackson CBOR dataformat library, specifically affecting versions prior to 2.11.4 and 2.12.1. This flaw resides in the com.fasterxml.jackson.dataformat:jackson-dataformat-cbor package and demonstrates a classic example of unchecked buffer allocation that can lead to denial of service conditions. The vulnerability stems from the library's failure to properly validate or constrain buffer size allocations during CBOR data processing, creating an avenue for malicious actors to exploit memory exhaustion scenarios.
The technical root cause of this vulnerability maps directly to CWE-129, which addresses improper validation of buffer size inputs. When processing CBOR (Concise Binary Object Representation) formatted data, the affected Jackson library performs unchecked allocation of byte buffers without adequate bounds checking on the size parameters provided in the input data. This allows an attacker to craft specially malformed CBOR payloads that specify artificially large buffer sizes, causing the Java Virtual Machine to attempt allocation of excessive memory blocks. The flaw occurs during deserialization operations where the library processes incoming CBOR data structures without proper size validation, leading to uncontrolled memory consumption.
The operational impact of this vulnerability extends beyond simple resource exhaustion, as it can be leveraged to execute denial of service attacks against applications that rely on Jackson for CBOR processing. When a java.lang.OutOfMemoryError exception is triggered, it can cause the entire application process to crash or become unresponsive, effectively rendering the service unavailable to legitimate users. This vulnerability particularly affects web applications, microservices, and backend systems that process external CBOR data from untrusted sources, making it a significant concern for enterprise environments where such processing is common. The attack vector is straightforward - an attacker simply needs to provide malformed CBOR data containing oversized buffer size indicators to trigger the memory exhaustion condition.
From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004, which covers "Endpoint Denial of Service" through resource exhaustion attacks. The flaw can be exploited in various attack scenarios including automated scanning tools that probe for vulnerable systems, or targeted attacks against specific applications that process CBOR data. Organizations using affected versions of Jackson dataformat should prioritize immediate patching, as the vulnerability does not require authentication or specialized privileges to exploit. The fix implemented in versions 2.11.4 and 2.12.1 involves adding proper bounds checking to buffer allocation operations, ensuring that buffer sizes are validated against reasonable maximum limits before memory allocation occurs. Security teams should also consider implementing input validation at network boundaries and monitoring for unusual memory consumption patterns that might indicate exploitation attempts.