CVE-2025-32029 in ts-asn1-der
Summary
by MITRE • 04/08/2025
ts-asn1-der is a collection of utility classes to encode ASN.1 data following DER rule. Incorrect number DER encoding can lead to denial on service for absolute values in the range 2**31 -- 2**32 - 1. The arithmetic in the numBitLen didn't take into account that values in this range could result in a negative result upon applying the >> operator, leading to an infinite loop. The issue is patched in version 1.0.4. If upgrading is not an option, the issue can be mitigated by validating inputs to Asn1Integer to ensure that they are not smaller than -2**31 + 1 and no larger than 2**31 - 1.
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Analysis
by VulDB Data Team • 04/08/2025
The vulnerability identified as CVE-2025-32029 affects the ts-asn1-der library, a collection of utility classes designed for encoding ASN.1 data according to DER (Distinguished Encoding Rules) standards. This library serves critical functions in cryptographic applications and data serialization where strict encoding rules must be maintained. The flaw manifests in the numBitLen function which is responsible for calculating the bit length of numbers during ASN.1 encoding operations. When processing absolute values within the range of 2^31 to 2^32 - 1, the arithmetic implementation fails to properly handle the signed bit shifting operation that occurs during the bit length calculation.
The technical root cause stems from improper handling of integer arithmetic in the numBitLen function where the right shift operator (>>) produces unexpected negative results when applied to values in the specified range. This arithmetic anomaly triggers an infinite loop condition that consumes system resources and leads to denial of service. The vulnerability specifically exploits the behavior of signed integer operations where values exceeding 2^31-1 when subjected to right bit shifting operations produce negative intermediate results that cause the loop termination condition to never be met. This represents a classic example of integer overflow and underflow issues that commonly affect cryptographic libraries and encoding utilities.
The operational impact of this vulnerability extends beyond simple resource exhaustion, as it can effectively disable applications relying on ts-asn1-der for ASN.1 encoding operations. Attackers can craft malicious inputs that trigger the infinite loop condition, causing system instability and potential application crashes. This denial of service scenario is particularly concerning in environments where ASN.1 encoding is frequently used for security protocols, certificate handling, or cryptographic operations. The vulnerability affects systems where the library is used for processing data that may contain large integer values, potentially disrupting services that depend on reliable encoding functionality.
Mitigation strategies for CVE-2025-32029 focus on both immediate and long-term solutions. The recommended approach involves upgrading to version 1.0.4 which contains the patched implementation of the numBitLen function that properly handles the edge case conditions. Organizations unable to perform immediate upgrades should implement input validation measures that restrict Asn1Integer values to the range of -2^31 + 1 to 2^31 - 1, effectively preventing the problematic arithmetic operations from occurring. This input sanitization approach aligns with defensive programming practices and follows the principle of least privilege in system security. The vulnerability classification aligns with CWE-191, Integer Underflow (Wrap or Wraparound), and could be mapped to ATT&CK technique T1499.004 for Network Denial of Service. Organizations should also consider implementing monitoring for unusual processing patterns that might indicate exploitation attempts and establish incident response procedures for handling such denial of service conditions.