Medium severity · published Jul 8, 2026
CVE-2026-42505
Invoking Encrypted Client Hello privacy leak in crypto/tls
5.3
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 32% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CR
crypto/tls · Go standard library
before 1.25.12; 1.26.0-0 before 1.26.5; 1.27.0-0 before 1.27.0-rc.2 · source: vendor
GO
GO · Golang
1.23.0 before 1.25.12; 1.26.0 before 1.26.5; 1.27 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-42505
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-42505
Patch
https://go.dev/cl/775960
Issue Tracking
https://go.dev/issue/79282
Mailing List
https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc
Vendor Advisory
https://pkg.go.dev/vuln/GO-2026-5856
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