Mitigation Strategies

The vulnerability arises from improper handling of the AES-GCM authentication tag length in CMS parsing within gpgsm. To mitigate this, it is recommended to update to a version of GnuPG that addresses this issue once available.

Additionally, cryptographic systems should minimize attacker-controlled parameters in ciphertexts and rely on secure key management practices to prevent manipulation of critical parameters like tag length.

Monitoring for updates and applying patches from the official GnuPG project is advised. The official GnuPG download page provides the latest stable releases and security updates.

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Executive Summary

CVE-2026-57062 is a vulnerability in the CMS (Cryptographic Message Syntax) parsing component of gpgsm in GnuPG up to version 2.5.20. The issue arises because the AES-GCM authentication tag length (aes-ICVlen) is supposed to be 12 bytes, but the parser incorrectly accepts a length of only 4 bytes.

This flaw allows an attacker to manipulate the ciphertext's authentication tag length, reducing the integrity protection and potentially enabling forgery or tampering with encrypted messages.

The root cause is that the tag length is treated as a tunable parameter controlled by the sender within the ciphertext, rather than a fixed property of the encryption algorithm and key.

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Impact Analysis

This vulnerability can impact you by weakening the integrity protection of encrypted messages processed by gpgsm in GnuPG. Because the authentication tag length can be reduced to as low as one byte, an attacker can more easily brute-force or manipulate the ciphertext.

As a result, attackers may be able to forge or tamper with encrypted communications, potentially leading to unauthorized data modification or bypassing security guarantees.

However, the CVSS base score is relatively low (2.9), indicating that exploitation requires local access with high attack complexity and no privileges, and it does not impact confidentiality or availability.

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Compliance Impact

CVE-2026-57062 involves a cryptographic weakness in the CMS parsing of AES-GCM in GnuPG's gpgsm, where the authentication tag length can be manipulated by an attacker. This reduces the integrity protection of encrypted data, potentially allowing tampering with ciphertext.

While the CVE description and resources do not explicitly mention compliance with standards such as GDPR or HIPAA, the vulnerability's impact on data integrity could undermine the security guarantees required by these regulations. Both GDPR and HIPAA mandate strong protections for data confidentiality and integrity, especially for sensitive personal or health information.

Therefore, exploitation of this vulnerability could lead to non-compliance risks by weakening cryptographic assurances, potentially exposing organizations to regulatory penalties if sensitive data integrity is compromised.

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