CVE-2026-59885: pyasn1: Quadratic complexity in OBJECT IDENTIFIER and RELATIVE-OID processing allows denial of service

highCVSS 7.5CVE-2026-59885

CSIRTS triage

vendor: pyasn1 product: pyasn1 Denial of serviceaffected: < 0.5.0

What: Quadratic complexity in processing OBJECT IDENTIFIER and RELATIVE-OID can lead to denial of service.
Who is affected: Users of pyasn1 versions before 0.5.0 are affected.
Urgency: This is a high urgency issue due to its high severity and potential for exploitation.
Action: Upgrade to pyasn1 version 0.5.0 or later.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.5
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-59885

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-598850.34% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 26% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-59885	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for pyasn1

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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highGHSA-8ppf-4f7h-5ppj: pyasn1: Quadratic complexity in OBJECT IDENTIFIER and RELATIVE-OID processing allows deni…ghsa · 2026-07-21
highGHSA-m4p7-r5rc-7g4j: pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDsghsa · 2026-07-21
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highCVE-2026-59885: pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the BER, CER, and DER decoders p…nvd · 2026-07-14