CVE-2026-27452 Overview
CVE-2026-27452 is an information disclosure vulnerability in the ASN.1 TypeScript ESM library (asn1-ts), which provides codecs for Basic Encoding Rules (BER) and Distinguished Encoding Rules (DER). In versions 11.0.5 and below, decoding an INTEGER value can inadvertently leak the contents of the underlying ArrayBuffer, potentially exposing sensitive data that was previously stored in memory.
Critical Impact
This vulnerability allows remote attackers to potentially access sensitive information from memory through crafted ASN.1 INTEGER values, creating a significant data exposure risk in applications processing untrusted ASN.1 data.
Affected Products
- asn1-ts versions 11.0.5 and below
- Applications using asn1-ts for BER/DER decoding operations
- Node.js and browser-based applications processing ASN.1 encoded data
Discovery Timeline
- 2026-02-21 - CVE CVE-2026-27452 published to NVD
- 2026-02-23 - Last updated in NVD database
Technical Details for CVE-2026-27452
Vulnerability Analysis
This vulnerability is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). The flaw exists in the INTEGER decoding functionality of the asn1-ts library. When processing certain INTEGER values, the library fails to properly isolate the decoded data from the underlying ArrayBuffer, which may contain residual data from previous memory allocations.
ArrayBuffer objects in JavaScript represent fixed-length raw binary data buffers. When an ArrayBuffer is created or reused, it may retain data from previous operations. The asn1-ts library's INTEGER decoder, in affected versions, creates views into ArrayBuffers without properly ensuring that only the intended bytes are accessible, potentially allowing access to adjacent memory contents.
The vulnerability can be triggered remotely by sending specially crafted ASN.1 encoded data to an application using the vulnerable library. Since ASN.1 encoding is commonly used in cryptographic protocols, certificate parsing, and secure communications (including X.509 certificates, LDAP, SNMP, and other protocols), the attack surface for this vulnerability can be substantial.
Root Cause
The root cause is improper bounds handling when creating typed array views over ArrayBuffer objects during INTEGER decoding operations. The library does not adequately constrain the view to only the bytes representing the decoded INTEGER value, potentially exposing additional bytes from the underlying buffer that may contain sensitive information from prior operations.
Attack Vector
The attack vector is network-based, requiring no authentication or user interaction. An attacker can exploit this vulnerability by sending maliciously crafted ASN.1 encoded data to any application that uses the vulnerable asn1-ts library for decoding. The attack does not require any privileges and can be executed remotely against any exposed endpoint that processes ASN.1 data.
Potential attack scenarios include:
- Sending crafted certificates or certificate requests to web servers
- Targeting LDAP directory services that process ASN.1 encoded queries
- Exploiting applications that parse ASN.1 data from untrusted sources
The vulnerability manifests in the INTEGER decoding function where ArrayBuffer views are created without proper boundary constraints. For detailed technical analysis, see the GitHub Security Advisory.
Detection Methods for CVE-2026-27452
Indicators of Compromise
- Unusual patterns of ASN.1 encoded requests with malformed INTEGER values
- Repeated decoding operations that return more data than expected for INTEGER types
- Memory inspection revealing sensitive data leakage in responses
- Anomalous traffic patterns targeting ASN.1 processing endpoints
Detection Strategies
- Implement application-level logging for ASN.1 decoding operations to detect unusual INTEGER values
- Monitor for responses containing unexpected amounts of data following INTEGER decoding
- Deploy SentinelOne Singularity to detect memory-based information disclosure attacks
- Use runtime application self-protection (RASP) to monitor library behavior
Monitoring Recommendations
- Enable detailed logging for all ASN.1 parsing operations in affected applications
- Monitor network traffic for unusually large responses from ASN.1 processing endpoints
- Implement data loss prevention (DLP) controls to detect potential information leakage
- Configure alerts for repeated failed or anomalous ASN.1 decoding attempts
How to Mitigate CVE-2026-27452
Immediate Actions Required
- Upgrade asn1-ts library to version 11.0.6 or later immediately
- Audit applications to identify all instances of asn1-ts library usage
- Implement input validation for ASN.1 data before processing
- Consider temporarily disabling or restricting access to endpoints that process untrusted ASN.1 data
Patch Information
The vulnerability is expected to be fixed in asn1-ts version 11.0.6. Organizations should update their dependencies as soon as the patched version becomes available. Review the GitHub Security Advisory for the latest patch status and upgrade instructions.
For npm-based projects, update the dependency by modifying package.json to require version 11.0.6 or higher, then run your package manager's update command.
Workarounds
- Implement strict input validation to reject malformed ASN.1 INTEGER values before they reach the vulnerable decoder
- Add application-layer bounds checking when handling decoded INTEGER data to prevent leakage
- Isolate ASN.1 processing in sandboxed environments to limit potential data exposure
- Restrict network access to ASN.1 processing endpoints to trusted sources only
# Update asn1-ts to patched version
npm update asn1-ts@^11.0.6
# Verify installed version
npm list asn1-ts
# For yarn users
yarn upgrade asn1-ts@^11.0.6
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
