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PatchSiren cyber security CVE debrief

CVE-2026-27137 Golang CVE debrief

CVE-2026-27137 is a high-severity vulnerability in the Go programming language. The vulnerability occurs when verifying a certificate chain containing multiple email address constraints with common local portions but different domain portions. In such cases, the constraints are not properly applied, and only the last constraint is considered. This vulnerability has a CVSS score of 7.5 and a HIGH severity rating. The CVE was published on March 6, 2026, and last modified on June 30, 2026. The vulnerability affects Go version 1.26.0.

Vendor
Golang
Product
Go
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-03-06
Original CVE updated
2026-09-16
Advisory published
2026-03-06
Advisory updated
2026-09-16

Who should care

Organizations and developers using the Go programming language should be aware of this vulnerability. Specifically, those who use Go for cryptographic operations, such as certificate verification, should take action to mitigate this vulnerability. Additionally, security teams and administrators responsible for maintaining Go-based systems should prioritize patching and monitoring.

Technical summary

The vulnerability is caused by improper handling of multiple email address constraints in a certificate chain. When verifying a certificate chain, the Go library fails to properly apply multiple constraints with common local portions but different domain portions. As a result, only the last constraint is considered, potentially allowing malicious certificates to be accepted. The vulnerability has a CVSS vector of CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, indicating a high severity rating.

Defensive priority

High priority should be given to patching and mitigating this vulnerability, especially in systems that perform cryptographic operations or rely on certificate verification. Developers and administrators should review their Go dependencies and update to a patched version as soon as possible.

Recommended defensive actions

  • Review and update Go dependencies to a patched version
  • Implement additional monitoring and logging for certificate verification
  • Consider compensating controls, such as certificate pinning or additional validation
  • Review and update cryptographic configurations and protocols
  • Perform thorough vulnerability scanning and risk assessments

Evidence notes

The CVE record and NVD detail provide official information about the vulnerability. The source item URL provides additional metadata and references. The vendor advisory and release notes offer guidance on mitigation and patching.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-27137 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-27137

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-27137 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-27137

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.