CVE-2012-3461 in libotr
Summary
by MITRE
The (1) otrl_base64_otr_decode function in src/b64.c; (2) otrl_proto_data_read_flags and (3) otrl_proto_accept_data functions in src/proto.c; and (4) decode function in toolkit/parse.c in libotr before 3.2.1 allocates a zero-length buffer when decoding a base64 string, which allows remote attackers to cause a denial of service (application crash) via a message with the value "?OTR:===.", which triggers a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 12/12/2021
The vulnerability described in CVE-2012-3461 represents a critical heap-based buffer overflow issue affecting the libotr library version 3.2.0 and earlier. This flaw manifests in multiple functions within the library's core components including otrl_base64_otr_decode in src/b64.c, otrl_proto_data_read_flags and otrl_proto_accept_data in src/proto.c, and the decode function in toolkit/parse.c. The vulnerability stems from improper handling of base64 string decoding operations where the library allocates a zero-length buffer when processing specific malformed input sequences. This particular input sequence "?OTR:===." triggers the problematic code path by causing the library to attempt to allocate memory for a buffer that has zero size, leading to memory allocation failures and subsequent application crashes.
The technical implementation of this vulnerability involves the library's failure to properly validate input parameters before proceeding with memory allocation operations. When the base64 decoding functions encounter the specific malformed string "?OTR:===.", they incorrectly calculate the required buffer size as zero, resulting in an allocation of a zero-length memory block. This allocation pattern creates a condition where subsequent memory operations attempt to write data to a zero-sized buffer, causing heap corruption and ultimately leading to application termination. The vulnerability demonstrates a classic buffer overflow scenario where improper bounds checking and input validation lead to memory management errors that can be exploited remotely.
From an operational impact perspective, this vulnerability creates significant denial of service risks for applications that rely on libotr for secure messaging functionality. The remote exploitation capability means that attackers can trigger system crashes without requiring local access or authentication, making it particularly dangerous in networked environments where the library is used for communication protocols. The vulnerability affects any application using libotr versions prior to 3.2.1, including instant messaging clients, secure communication tools, and any software implementing the Off-the-Record Messaging protocol. The heap-based nature of the overflow also raises concerns about potential information disclosure or privilege escalation if the vulnerability were to be chained with other exploits, though the primary impact remains denial of service.
The vulnerability aligns with CWE-122, which describes heap-based buffer overflow conditions, and demonstrates characteristics consistent with ATT&CK technique T1499.004 for network denial of service attacks. Organizations using affected versions of libotr should prioritize immediate patching to version 3.2.1 or later, as this update addresses the core memory allocation issues in the base64 decoding functions. Additional mitigations include implementing input validation layers in applications that use libotr, monitoring for unusual memory allocation patterns, and ensuring proper error handling in messaging protocols. The vulnerability highlights the importance of robust input validation and memory management practices in cryptographic libraries, where improper handling of malformed data can lead to critical system failures that compromise availability and service integrity.