CVE-2026-1005 Integer Underflow in AES-GCM/CCM/ARIA-GCM Decryption

CVE-2026-1005 describes an integer underflow vulnerability within a Microsoft product’s implementation of AES-GCM, CCM, and ARIA-GCM decryption algorithms. This flaw allows an attacker to trigger an out-of-bounds memory access. While the specific product affected is not detailed in the provided source, the vulnerability lies within the cryptographic functions used for data decryption, indicating a potential impact on confidentiality and integrity. Successful exploitation could allow an attacker to execute arbitrary code or disclose sensitive information. Given the widespread use of these encryption algorithms, this vulnerability poses a significant risk.

Attack Chain

1. Attacker identifies a system utilizing the vulnerable Microsoft product and its AES-GCM/CCM/ARIA-GCM decryption implementation.
2. Attacker crafts a malicious input designed to trigger the integer underflow during the decryption process.
3. The crafted input is sent to the vulnerable system for decryption. This could be via a network protocol, file processing, or other data ingestion method.
4. The vulnerable decryption routine processes the input, leading to an integer underflow.
5. The integer underflow results in an out-of-bounds memory access during the decryption operation.
6. This out-of-bounds memory access allows the attacker to read sensitive data from memory locations outside the intended buffer.
7. Alternatively, the attacker leverages the out-of-bounds write to overwrite critical data structures or executable code within the process’s memory space.
8. If code is overwritten, the attacker gains arbitrary code execution within the context of the vulnerable process.

Impact

Successful exploitation of CVE-2026-1005 could lead to unauthorized information disclosure, allowing attackers to steal sensitive data that was intended to be protected by encryption. In a more severe scenario, the vulnerability can be leveraged for arbitrary code execution, enabling attackers to gain control over the affected system. The lack of specific product information makes it difficult to quantify the exact number of potential victims, but the vulnerability’s presence in widely used cryptographic functions implies a broad impact across various sectors and applications.

Recommendation

• Monitor for unexpected memory access patterns in processes performing AES-GCM/CCM/ARIA-GCM decryption, using a host-based intrusion detection system (HIDS).
• Deploy the Sigma rule “Detect Potential Exploitation of CVE-2026-1005” to identify suspicious processes that might be exploiting the vulnerability.
• Apply any available patches or updates released by Microsoft to address CVE-2026-1005 as soon as they are released.