CVE-2026-27137— Incorrect enforcement of email constraints in crypto/x509
Quick assessment
Affected
Go standard library crypto/x509
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
Google Go是美国谷歌（Google）公司的一种静态强类型、编译型、并发型，并具有垃圾回收功能的编程语言。 Google Go存在安全漏洞，该漏洞源于验证包含多个电子邮件地址约束的证书链时，约束应用不当，可能导致仅考虑最后一个约束。
Possible ATT&CK Techniques 1 AI
T1190 · Exploit Public-Facing ApplicationAffected Version Matrix 1
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Go standard library | crypto/x509 | 1.26.0-0< 1.26.1 |
affected |
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I. Basic Information for CVE-2026-27137
Vulnerability Information
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Vulnerability Title
Incorrect enforcement of email constraints in crypto/x509
Source: CVE Program / CVE List V5
Vulnerability Description
When verifying a certificate chain which contains a certificate containing multiple email address constraints which share common local portions but different domain portions, these constraints will not be properly applied, and only the last constraint will be considered.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Google Go 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Google Go是美国谷歌（Google）公司的一种静态强类型、编译型、并发型，并具有垃圾回收功能的编程语言。 Google Go存在安全漏洞，该漏洞源于验证包含多个电子邮件地址约束的证书链时，约束应用不当，可能导致仅考虑最后一个约束。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Go standard library | crypto/x509 | 1.26.0-0 ~ 1.26.1 | - |
|
II. Public POCs for CVE-2026-27137
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-27137 (1)
Vendor Advisories for CVE-2026-27137 (1)
Vendor Pages for CVE-2026-27137 (1)
Other References for CVE-2026-27137 (1)
Same Patch Batch · Go standard library · 2026-03-06 · 5 CVEs total
| CVE-2026-25679 | Incorrect parsing of IPv6 host literals in net/url | |
| CVE-2026-27138 | Panic in name constraint checking for malformed certificates in crypto/x509 | |
| CVE-2026-27142 | URLs in meta content attribute actions are not escaped in html/template | |
| CVE-2026-27139 | FileInfo can escape from a Root in os |
IV. Related Vulnerabilities
Same product: crypto/x509
-
CVE-2026-27145
Inefficient candidate hostname parsing in crypto/x509 -
CVE-2026-32280
Unexpected work during chain building in crypto/x509 -
CVE-2026-32281
Inefficient policy validation in crypto/x509 -
CVE-2026-33810
Case-sensitive excludedSubtrees name constraints cause Auth -
CVE-2026-27138
Panic in name constraint checking for malformed certificates
Same vendor: Go standard library
-
CVE-2026-56860
Avoid quadratic complexity in resolvePath in net/url -
CVE-2026-56859
Add recursion depth guard during decode in encoding/xml -
CVE-2026-33818
Enforce maximum recursion depth in encoding/asn1 -
CVE-2026-56853
Apply ReadHeaderTimeout when doing unencrypted HTTP/2 check -
CVE-2026-56862
Limit handshake messages we are willing to accept post-hands
V. Comments for CVE-2026-27137
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