CVE-2016-2195 in Botan
Summary
by MITRE
Integer overflow in the PointGFp constructor in Botan before 1.10.11 and 1.11.x before 1.11.27 allows remote attackers to overwrite memory and possibly execute arbitrary code via a crafted ECC point, which triggers a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 08/19/2022
The vulnerability identified as CVE-2016-2195 represents a critical integer overflow flaw within the Botan cryptographic library that affects versions prior to 1.10.11 and 1.11.27. This vulnerability specifically resides in the PointGFp constructor which handles elliptic curve cryptography operations over finite fields. The flaw manifests when processing crafted elliptic curve points that trigger an integer overflow condition during memory allocation calculations. The vulnerability is categorized under CWE-190 as an integer overflow or wraparound, which occurs when a calculation produces a result that exceeds the maximum value that can be represented by the target data type. The issue stems from improper validation of input parameters during the construction of elliptic curve points, particularly when dealing with the x and y coordinates of points on the curve.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially enable remote code execution through heap-based buffer overflow conditions. When an attacker crafts a malicious elliptic curve point with carefully manipulated coordinates, the PointGFp constructor performs calculations that result in insufficient memory allocation for the point structure. This insufficient allocation creates a situation where subsequent operations attempt to write beyond the allocated memory boundaries, leading to heap corruption that can be exploited to overwrite adjacent memory locations. The vulnerability operates under the ATT&CK framework as a code injection technique, specifically leveraging memory corruption to achieve arbitrary code execution. The attack vector requires a remote attacker to send a specially crafted ECC point to a vulnerable system, making it particularly dangerous in networked environments where cryptographic libraries handle external inputs.
The technical exploitation of CVE-2016-2195 relies on the predictable nature of integer overflow in the memory allocation logic. During elliptic curve point construction, the library calculates the required buffer size based on input parameters without proper overflow checking. When the input point coordinates are crafted to cause integer overflow during size calculations, the resulting allocation becomes insufficient for the actual data structure that needs to be stored. This misalignment between allocated and required memory space creates opportunities for attackers to manipulate heap metadata and control execution flow. The vulnerability affects the core cryptographic operations of the Botan library, making it particularly dangerous for systems that rely on elliptic curve cryptography for secure communications, digital signatures, and key exchange mechanisms. The flaw demonstrates the critical importance of input validation in cryptographic libraries where malformed inputs can lead to fundamental security breaches.
Mitigation strategies for CVE-2016-2195 involve immediate patching of affected Botan library versions to the patched releases 1.10.11 and 1.11.27 which contain proper integer overflow checks in the PointGFp constructor. Organizations should also implement network segmentation and access controls to limit exposure to potential attackers who might attempt to exploit this vulnerability. Additional defensive measures include monitoring network traffic for suspicious ECC point constructions and implementing proper input validation at application layers that use the Botan library. The vulnerability highlights the necessity of comprehensive testing for integer overflow conditions in cryptographic libraries and adherence to secure coding practices that prevent such memory safety issues. Security teams should also consider implementing runtime protections such as stack canaries and address space layout randomization to make exploitation more difficult even if the underlying vulnerability persists in other components.