CVE-2026-23490
Published: 16 January 2026
Summary
CVE-2026-23490 is a high-severity Allocation of Resources Without Limits or Throttling (CWE-770) vulnerability in Pyasn1 Pyasn1. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 9.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SI-10 (Information Input Validation).
Deeper analysis
CVE-2026-23490 is a denial-of-service vulnerability in pyasn1, a generic ASN.1 library for Python, affecting versions prior to 0.6.2. The issue arises from processing a malformed RELATIVE-OID with excessive continuation octets, leading to memory exhaustion. Published on 2026-01-16, it carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and is categorized under CWE-770 (Allocation of Resources Without Limits or Throttling).
An unauthenticated attacker can exploit this vulnerability remotely over the network with low attack complexity and no user interaction required. By supplying specially crafted input to an application using the vulnerable pyasn1 library, the attacker can trigger unbounded memory allocation, resulting in high-impact denial of service that exhausts system resources and disrupts service availability.
The vulnerability is addressed in pyasn1 version 0.6.2, where the fix is implemented via commit 3908f144229eed4df24bd569d16e5991ace44970. Official resources include the GitHub security advisory GHSA-63vm-454h-vhhq, release notes for v0.6.2, and a Debian LTS announcement detailing mitigation for affected distributions. Security practitioners should prioritize upgrading to the patched version.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-2865
Vulnerability details
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.2, a Denial-of-Service issue has been found that leads to memory exhaustion from malformed RELATIVE-OID with excessive continuation octets. This vulnerability is fixed in 0.6.2.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Direct match to application exploitation causing endpoint DoS via unbounded memory allocation from malformed input.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Mandates identification, reporting, and correction of flaws like the memory exhaustion in pyasn1 from malformed RELATIVE-OID, ensuring timely patching to version 0.6.2.
Requires validation of ASN.1 inputs to reject malformed RELATIVE-OID with excessive continuation octets, preventing unbounded memory allocation.
Employs denial-of-service protections such as resource limits and throttling to mitigate memory exhaustion attacks exploiting the pyasn1 vulnerability.