CVE intelligence

CVE-2026-59884

Vulnerability intelligence

Published Jul 14, 2026Sources checked Oct 27, 2026

7.5HIGHCVSS out of 10

What this means

Review the available evidence

CVE-2026-59884 and is rated High severity with a CVSS score of 7.5. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Jul 22, 2026

CBL-Mariner Releases

Vendor-listed releases

0.4.8-3

CISA KEVNot listedBased on the latest collected catalog

EPSS0.6%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-59884?

pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the BER decoder shared by the CER and DER codecs parses long-form tags by accumulating continuation octets without an upper bound on the tag ID size, allowing a crafted input to force construction of an arbitrarily large integer with CPU cost growing quadratically and to trigger unhandled ValueError exceptions in Python 3.11+ error formatting paths.

Any application decoding untrusted BER, CER, or DER input is affected. This issue is fixed in version 0.6.4.

Source: NVD