CVE-2026-2016 in libfastcommon
Summary
by MITRE • 02/06/2026
A security vulnerability has been detected in happyfish100 libfastcommon up to 1.0.84. Affected by this vulnerability is the function base64_decode of the file src/base64.c. The manipulation leads to stack-based buffer overflow. Local access is required to approach this attack. The exploit has been disclosed publicly and may be used. The identifier of the patch is 82f66af3e252e3e137dba0c3891570f085e79adf. Applying a patch is the recommended action to fix this issue.
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Analysis
by VulDB Data Team • 02/18/2026
The vulnerability identified as CVE-2026-2016 represents a critical stack-based buffer overflow in the happyfish100 libfastcommon library version 1.0.84 and earlier. This flaw exists within the base64_decode function located in the src/base64.c source file, making it a significant concern for systems that rely on this library for base64 encoding and decoding operations. The vulnerability stems from inadequate input validation and bounds checking during the base64 decoding process, which allows an attacker to manipulate the input data in a way that overflows the allocated stack buffer. The attack requires local access to the system, meaning that exploitation would need an attacker to already have user-level privileges or physical access to the target machine. This requirement significantly reduces the attack surface compared to remote exploits but does not eliminate the threat entirely, as local privilege escalation opportunities may still exist. The public disclosure of this exploit increases the risk level substantially, as threat actors can now leverage this vulnerability without requiring advanced reconnaissance or development efforts. The patch identifier 82f66af3e252e3e137dba0c3891570f085e79adf provides a specific reference point for the fix, which should be applied immediately to mitigate the risk. This vulnerability aligns with CWE-121 Stack-based Buffer Overflow, which is classified as a common weakness in software development practices. The operational impact of this vulnerability extends beyond simple denial of service, as it could potentially allow for arbitrary code execution if an attacker can control the overflowed memory region. The base64 decoding function is commonly used in various network protocols, file processing applications, and data transmission systems, making this vulnerability particularly dangerous in environments where such operations are frequent. According to ATT&CK framework, this vulnerability could be leveraged as part of a privilege escalation technique under the T1068 - Exploitation for Privilege Escalation tactic, where an attacker with local access might exploit the buffer overflow to gain elevated privileges. The patch implementation should be thoroughly tested in staging environments before deployment to ensure compatibility with existing applications that depend on libfastcommon. Organizations using this library should conduct immediate vulnerability assessments to identify all systems that may be exposed to this threat, particularly those running applications that process base64 encoded data from untrusted sources. The presence of this vulnerability in a widely-used library like libfastcommon means that numerous applications and systems may be affected, potentially creating a cascading security risk across interconnected environments. Security teams should monitor for any signs of exploitation attempts and implement network-based detection mechanisms to identify potential attacks targeting this specific vulnerability. The local access requirement does not eliminate the need for immediate remediation, as local attackers could include malicious insiders or attackers who have gained initial access through other means. The vulnerability demonstrates a fundamental flaw in input validation practices and highlights the importance of proper memory management in cryptographic and data processing functions. Organizations should review their entire software supply chain for similar vulnerabilities in other libraries and ensure that proper security testing and code review processes are in place to prevent such issues from occurring in the future.