CVE-2026-3336 in AWS-LC
Summary
by MITRE • 03/03/2026
Improper certificate validation in PKCS7_verify() in AWS-LC allows an unauthenticated user to bypass certificate chain verification when processing PKCS7 objects with multiple signers, except the final signer.
Customers of AWS services do not need to take action. Applications using AWS-LC should upgrade to AWS-LC version 1.69.0.
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Analysis
by VulDB Data Team • 03/09/2026
The vulnerability identified as CVE-2026-3336 represents a critical flaw in the AWS-LC cryptographic library that affects the PKCS7 certificate verification process. This issue specifically targets the PKCS7_verify() function which is responsible for validating certificate chains during cryptographic operations. The flaw manifests when processing PKCS7 objects that contain multiple signers, creating a scenario where certificate chain verification can be bypassed without proper authentication. The vulnerability is particularly concerning because it affects the final signer in multi-signer scenarios, potentially allowing malicious actors to manipulate certificate validation processes while maintaining the appearance of legitimate cryptographic operations.
The technical implementation of this vulnerability stems from improper handling of certificate chain validation logic within the AWS-LC library. When multiple signers are present in a PKCS7 structure, the verification process should rigorously validate each signer's certificate chain to ensure authenticity and integrity. However, the flaw allows the system to accept certificates that should have failed validation, particularly focusing on the final signer in the sequence. This represents a direct violation of cryptographic security principles and creates a pathway for man-in-the-middle attacks or certificate forgery scenarios. The vulnerability falls under CWE-295 which specifically addresses improper certificate validation and can be categorized under ATT&CK technique T1552.001 for credentials from password storage devices, as it undermines the trust model that cryptographic verification is designed to establish.
The operational impact of CVE-2026-3336 extends beyond simple certificate validation failures, potentially allowing attackers to bypass critical security controls that depend on proper certificate chain verification. Applications utilizing AWS-LC for cryptographic operations, particularly those handling sensitive data or implementing authentication mechanisms, may be vulnerable to attacks that exploit this flaw. The vulnerability affects systems where PKCS7 objects with multiple signers are processed, which includes various cryptographic protocols and security implementations. Organizations using AWS services directly do not need to take action since the vulnerability is contained within the AWS-LC library itself, but applications that directly integrate AWS-LC components must address this issue through immediate software updates.
The recommended mitigation strategy involves upgrading to AWS-LC version 1.69.0 which contains the necessary patches to address the certificate validation flaw. This upgrade should be prioritized across all applications and systems that depend on the affected cryptographic library. Security teams should conduct thorough assessments of their cryptographic implementations to identify any potential dependencies on the vulnerable PKCS7_verify() function. Additionally, organizations should implement monitoring for any unusual certificate validation patterns or authentication failures that might indicate exploitation attempts. The patch addresses the root cause by implementing proper certificate chain validation logic that ensures all signers in multi-signer PKCS7 objects are properly authenticated before accepting the cryptographic operations as valid. This remediation aligns with industry best practices for cryptographic library maintenance and security patch management as outlined in NIST SP 800-57 and ISO/IEC 15408 standards.