CVE-2026-42505
Invoking Encrypted Client Hello privacy leak in crypto/tls
Description
Handshakes which used Encrypted Client Hello could be de-anonymized by a passive network observer due to a disclosure of pre-shared key identities in the unencrypted client hello.
INFO
Published Date :
July 8, 2026, 5:17 p.m.
Last Modified :
July 13, 2026, 5:05 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
Solution
- Disable Encrypted Client Hello.
- Update TLS configurations.
- Review key exchange mechanisms.
Public PoC/Exploit Available at Github
CVE-2026-42505 has a 3 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-42505.
| URL | Resource |
|---|---|
| https://go.dev/cl/775960 | Patch |
| https://go.dev/issue/79282 | Issue Tracking Patch |
| https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc | Mailing List Release Notes Vendor Advisory |
| https://pkg.go.dev/vuln/GO-2026-5856 | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-42505 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-42505
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Gin (golang) skill for AI Agents.
None
Dockerfile
ExternalDNS Webhook Provider for Poweradmin
Dockerfile Makefile Go Shell
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-42505 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-42505 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jul. 13, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:golang:go:*:*:*:*:*:*:*:* versions up to (excluding) 1.25.12 *cpe:2.3:a:golang:go:*:*:*:*:*:*:*:* versions from (including) 1.26.0 up to (excluding) 1.26.5 *cpe:2.3:a:golang:go:1.27:rc1:*:*:*:*:*:* Added Reference Type Go Project: https://go.dev/cl/775960 Types: Patch Added Reference Type Go Project: https://go.dev/issue/79282 Types: Issue Tracking, Patch Added Reference Type Go Project: https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc Types: Mailing List, Release Notes, Vendor Advisory Added Reference Type Go Project: https://pkg.go.dev/vuln/GO-2026-5856 Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 08, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N Added CWE CWE-201 Added SSVC {'id': 'CVE-2026-42505', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-08T18:03:53.821942Z'} -
New CVE Received by [email protected]
Jul. 08, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Go standard library', 'product': 'crypto/tls', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '1.25.12', 'versionType': 'semver'}, {'status': 'affected', 'version': '1.26.0-0', 'lessThan': '1.26.5', 'versionType': 'semver'}, {'status': 'affected', 'version': '1.27.0-0', 'lessThan': '1.27.0-rc.2', 'versionType': 'semver'}], 'packageName': 'crypto/tls', 'collectionURL': 'https://pkg.go.dev', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': 'clientHelloMsg.marshalMsg'}, {'name': 'Conn.Handshake'}, {'name': 'Conn.HandshakeContext'}, {'name': 'Conn.Read'}, {'name': 'Conn.Write'}, {'name': 'Dial'}, {'name': 'DialWithDialer'}, {'name': 'Dialer.Dial'}, {'name': 'Dialer.DialContext'}, {'name': 'QUICConn.HandleData'}, {'name': 'QUICConn.SendSessionTicket'}, {'name': 'QUICConn.Start'}]}] Added Description Handshakes which used Encrypted Client Hello could be de-anonymized by a passive network observer due to a disclosure of pre-shared key identities in the unencrypted client hello. Added Reference https://go.dev/cl/775960 Added Reference https://go.dev/issue/79282 Added Reference https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc Added Reference https://pkg.go.dev/vuln/GO-2026-5856