The vulnerability identified as CVE-2026-27452 affects the JonathanWilbur asn1-ts library, a TypeScript implementation for ASN.1 encoding and decoding, specifically supporting Basic Encoding Rules (BER) and Distinguished Encoding Rules (DER). In versions 11.0.5 and earlier, the decoding process for ASN.1 INTEGER types can inadvertently leak the underlying ArrayBuffer that holds the encoded data. This leakage constitutes an exposure of sensitive information (CWE-200) because the internal memory buffer may contain confidential data beyond the intended INTEGER value. The flaw arises due to improper memory handling or insufficient data sanitization during the decoding routine, allowing an attacker who can supply crafted ASN.1 data to retrieve unintended memory contents. The vulnerability is remotely exploitable without any authentication or user interaction, increasing its severity. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N) reflects a network attack vector with low complexity, no privileges or user interaction required, and a high confidentiality impact, while integrity and availability remain unaffected. This vulnerability is particularly critical for applications relying on asn1-ts for parsing ASN.1 data in security-sensitive contexts such as cryptographic protocols, certificate parsing, or secure communications. The issue is slated to be fixed in version 11.0.6, but no patch links are currently provided. No known exploits have been reported in the wild as of the publication date, but the high severity and ease of exploitation warrant immediate attention.

The primary impact of CVE-2026-27452 is the unauthorized disclosure of sensitive information due to leakage of internal memory buffers during ASN.1 INTEGER decoding. This can lead to exposure of cryptographic keys, personal data, or other confidential information embedded in ASN.1 structures. Organizations using the asn1-ts library in security-critical applications such as certificate validation, cryptographic key handling, or secure messaging may face significant confidentiality breaches. The vulnerability does not affect data integrity or availability, but the loss of confidentiality can undermine trust and security guarantees, potentially leading to further attacks or compliance violations. Because exploitation requires only network access and no authentication, attackers can remotely target vulnerable systems, increasing the risk of widespread data leaks. The scope includes any software or services that incorporate asn1-ts versions 11.0.5 or earlier, which may be embedded in web services, cloud platforms, or client applications worldwide. The absence of known exploits in the wild does not reduce the urgency, as proof-of-concept exploits could be developed rapidly given the straightforward nature of the flaw.

To mitigate CVE-2026-27452, organizations should immediately audit their software dependencies to identify any usage of the JonathanWilbur asn1-ts library at version 11.0.5 or below. The primary mitigation is to upgrade to version 11.0.6 or later once it becomes available, as this version is expected to contain the fix for the memory leakage issue. If an immediate upgrade is not feasible, consider implementing input validation and sanitization on ASN.1 data before decoding to reduce the risk of crafted malicious inputs. Additionally, isolate or sandbox components that perform ASN.1 decoding to limit the impact of potential data leakage. Monitoring network traffic for unusual ASN.1 data patterns and employing runtime application self-protection (RASP) techniques can help detect exploitation attempts. Finally, ensure that sensitive data is not unnecessarily stored or processed in ASN.1 INTEGER fields to minimize exposure. Regularly review and update software supply chain security practices to quickly respond to such vulnerabilities in third-party libraries.