CVE-2019-25049 in LibreSSL
Summary
by MITRE • 07/01/2021
LibreSSL 2.9.1 through 3.2.1 has an out-of-bounds read in asn1_item_print_ctx (called from asn1_template_print_ctx).
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Analysis
by VulDB Data Team • 07/04/2021
The vulnerability CVE-2019-25049 represents a critical out-of-bounds read flaw discovered in LibreSSL versions ranging from 2.9.1 through 3.2.1. This vulnerability resides within the ASN.1 parsing functionality of the cryptographic library, specifically in the asn1_item_print_ctx function which is invoked by asn1_template_print_ctx. The issue manifests when processing malformed ASN.1 encoded data structures during certificate or cryptographic object printing operations. The out-of-bounds read occurs due to insufficient bounds checking when traversing ASN.1 template structures, allowing an attacker to provide specially crafted input that causes the application to read memory beyond allocated buffers. This vulnerability falls under CWE-125, which specifically addresses out-of-bounds read conditions in software implementations.
The technical exploitation of this vulnerability requires an attacker to craft malicious ASN.1 formatted data that triggers the vulnerable code path during certificate or cryptographic object parsing and display operations. When the vulnerable function processes such malformed input, it attempts to access memory locations beyond the intended buffer boundaries, potentially leading to information disclosure or application instability. The attack surface includes any application that utilizes LibreSSL for processing certificates or ASN.1 encoded data, particularly web servers, mail servers, and cryptographic applications that perform certificate validation and display operations. This vulnerability directly impacts the integrity and availability of systems relying on LibreSSL's ASN.1 parsing capabilities.
The operational impact of CVE-2019-25049 extends beyond simple memory access violations, as it can potentially expose sensitive information from adjacent memory regions to attackers. In environments where LibreSSL is used for certificate validation, such as web servers handling HTTPS traffic or mail servers processing PKI certificates, this vulnerability could allow attackers to extract cryptographic keys, session tokens, or other sensitive data from memory. The vulnerability also poses a risk to application stability, as memory access violations can cause crashes or unexpected behavior in affected applications. Additionally, the vulnerability may enable more sophisticated attacks when combined with other memory corruption issues, as demonstrated in the ATT&CK framework's memory corruption techniques category.
Mitigation strategies for CVE-2019-25049 primarily involve upgrading to LibreSSL versions 3.2.2 or later, where the out-of-bounds read has been addressed through proper bounds checking in the ASN.1 parsing code. System administrators should prioritize patching affected systems, particularly those handling certificate processing or cryptographic operations. Organizations should also implement monitoring for unusual certificate processing patterns or application crashes that might indicate exploitation attempts. Network segmentation and access controls should be maintained to limit potential attack vectors, while regular security assessments should verify that all systems using LibreSSL have been updated to secure versions. The vulnerability serves as a reminder of the critical importance of proper input validation and bounds checking in cryptographic libraries, as these components often handle sensitive data and require robust protection against memory corruption attacks.