What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-14 · updated 2026-07-21
• Weakness: CWE-400

Description

pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the BER, CER, and DER decoders process OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs, so a small crafted payload containing an OID with many arcs consumes excessive CPU per decode() call and can deny service to applications that decode untrusted ASN.1 data. The corresponding encoders have the same quadratic behavior when an application re-encodes previously decoded attacker-supplied values. This issue is fixed in version 0.6.4.

Affected products

• pyasn1: before 0.6.4 — fixed in 0.6.4

How to fix

Upgrade to a fixed version: pyasn1 0.6.4. Check the vendor advisory for mitigations.

References

• https://github.com/pyasn1/pyasn1/commit/45bdb19eb7df4b3780fe9c912c63e99bffc39dd9
• https://github.com/pyasn1/pyasn1/releases/tag/v0.6.4
• https://github.com/pyasn1/pyasn1/security/advisories/GHSA-8ppf-4f7h-5ppj

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