CVE-2026-59885: pyasn1 algorithmic complexity denial of service in OID processing

CVE-2026-59885 · Severity: high · CVSS 7.5 · Published 2026-07-14

A vulnerability in the pyasn1 library, which is used to handle ASN.1 data for protocols like LDAP, SNMP, and Kerberos, can allow an attacker to crash or slow down an application. By sending a specially crafted small data package, an attacker can force the system to consume excessive CPU resources, leading to a denial of service. This can disrupt critical services that rely on digital certificates or secure network communications.

Technologies: Pyasn1, pyasn1 (PyPI). Vendors: Pyasn1, PyPI.

Quick answers

Is CVE-2026-59885 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-59885 being exploited in the wild.
How severe is CVE-2026-59885?
High severity, with a CVSS score of 7.5, published 14 July 2026.
Which products and versions are affected?
Pyasn1 < 0.6.4, <= 0.6.3; pyasn1 (PyPI) ECOSYSTEM:introduced=0,fixed=0.6.4.
Is there a fix for CVE-2026-59885?
Yes. pyasn1 (PyPI): upgrade to 0.6.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-59885 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-59885?
Check whether you run Pyasn1 or pyasn1 (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • pyasn1 (PyPI): upgrade to 0.6.4 or later
    pip install "pyasn1>=0.6.4"

Technical details

The BER/CER/DER decoders and encoders in pyasn1 (specifically ObjectIdentifierPayloadDecoder, RelativeOIDPayloadDecoder, and their encoder counterparts) process OID values in quadratic time relative to the number of arcs. An attacker can exploit this by providing a crafted ASN.1 payload (tens of kilobytes) containing an OID with a large number of arcs, causing the decode() or encode() calls to consume seconds of CPU time. This algorithmic complexity vulnerability (CWE-407) is not mitigated by previous arc-size limits which only bounded the byte length of individual arcs. The issue is fixed in version 0.6.4 by implementing linear-time arc accumulation.

Affected products

  • pyasn1 pyasn1 <= 0.6.3

Identifiers

  • CVE-2026-59885
  • GHSA-8ppf-4f7h-5ppj
  • PYSEC-2026-3456

Timeline

  • 2026-07-09: disclosed: Vulnerability reported and published to GitHub repository
  • 2026-07-14: advisory: Published to the National Vulnerability Database (NVD)
  • 2026-07-21: advisory: GitHub Advisory GHSA-8ppf-4f7h-5ppj published
  • 2026-07-21: patched: Fixed in version 0.6.4

References

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