Medium 5.3Published Jul 8, 2026

CVE-2026-42505Invoking Encrypted Client Hello privacy leak in crypto/tls

Updated under an hour ago (Oct 27, 2026, 11:50 PM ET)

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It affects Go standard library crypto/tls and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for Go standard library crypto/tls

Exploited in the last 30 days

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: 5.3 MEDIUM (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness (CWE): CWE-201
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Go
NVD analysis: Analyzed
Record last updated: Jul 8, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Go standard library crypto/tls go_standard_library:crypto_tls (from the name)	before 1.25.12; from 1.26.0-0 before 1.26.5; 1.27.0-0 builds before 1.27.0-rc.2	CNA record
golang go golang:go	from 1.23.0 before 1.25.12; from 1.26.0 before 1.26.5; 1.27	NVD

References

References

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

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.