CVE-2026-32313 in xmlseclibs
Summary
by MITRE • 03/16/2026
xmlseclibs is a library written in PHP for working with XML Encryption and Signatures. Prior to 3.1.5, XML nodes encrypted with either aes-128-gcm, aes-192-gcm, or aes-256-gcm lack validation of the authentication tag length. An attacker can use this to brute-force an authentication tag, recover the GHASH key, and decrypt the encrypted nodes. It also allows to forge arbitrary ciphertexts without knowing the encryption key. This vulnerability is fixed in 3.1.5.
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Analysis
by VulDB Data Team • 03/21/2026
The vulnerability identified as CVE-2026-32313 affects the xmlseclibs PHP library, which serves as a critical component for implementing XML Encryption and Signatures in web applications. This library is widely used across the industry for securing sensitive data transmissions and ensuring data integrity in enterprise environments. The flaw resides in the implementation of authenticated encryption modes including aes-128-gcm, aes-192-gcm, and aes-256-gcm, where the authentication tag length validation is absent during the encryption process. The vulnerability stems from inadequate cryptographic implementation practices that violate fundamental security principles for authenticated encryption schemes.
The technical flaw represents a critical weakness in the cryptographic protocol implementation, specifically targeting the Galois/Counter Mode (GCM) authentication mechanism. In GCM mode, the authentication tag serves as a cryptographic checksum that ensures both the confidentiality and integrity of encrypted data. When the authentication tag length is not properly validated, attackers can exploit this gap to perform brute-force attacks against the authentication tag values. This vulnerability directly maps to CWE-310, which addresses cryptographic weaknesses related to insufficient validation of authentication tags. The flaw allows adversaries to recover the GHASH key component that is integral to GCM's security model, effectively undermining the entire encryption scheme.
The operational impact of this vulnerability extends far beyond simple data compromise, as it enables sophisticated attacks that can lead to complete system compromise. An attacker with access to encrypted XML nodes can potentially decrypt sensitive information without possessing the legitimate encryption keys, while simultaneously gaining the ability to forge arbitrary ciphertexts. This dual capability creates a severe threat landscape where both confidentiality and integrity assurances are completely compromised. The vulnerability affects any system utilizing xmlseclibs version prior to 3.1.5 for XML encryption operations, making it particularly dangerous in enterprise environments where sensitive data is routinely encrypted using these methods. This weakness can be exploited through various attack vectors including man-in-the-middle scenarios, insider threats, or compromised web applications.
The remediation strategy involves upgrading to xmlseclibs version 3.1.5 or later, which implements proper authentication tag length validation and addresses the cryptographic implementation flaw. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing affected library versions and prioritize immediate patching. Security teams should also implement monitoring for suspicious cryptographic operations and consider implementing additional security controls such as cryptographic key rotation and enhanced access controls. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and defense evasion, as attackers can bypass encryption protections while maintaining stealth. The fix addresses the underlying cryptographic implementation weakness through proper validation of authentication tag parameters, ensuring that the GCM mode operates within its intended security parameters and maintains the integrity guarantees that authenticated encryption schemes are designed to provide.