CVE-2026-42505

Invoking Encrypted Client Hello privacy leak in crypto/tls

MEDIUM

5.3

CVSS Score

Published: July 8, 2026 at 03:46 PM UTC

Updated: October 25, 2026 at 05:10 PM UTC

2 products affected across 2 vendorsGoGo

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Severity

MEDIUM5.3

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Go · Golang

95%

1.23.0 ≤ v < 1.25.121.26.0 ≤ v < 1.26.51.27 1.27 rc1

Affected range stops below 1.25.12, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.26.5, so it looks safe — our inference, not a vendor statement

Go · Go Standard Librarygo

90%

v < 1.25.121.26.0-0 ≤ v < 1.26.51.27.0-0 ≤ v < 1.27.0-rc.21.26.0-0 1.27.0-0

Affected range stops below 1.25.12, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.26.5, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.27.0-rc.2, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (4)

Patch

Source: cverecord

https://go.dev/cl/775960

Issue TrackingPatch

Source: cverecord

https://go.dev/issue/79282

Mailing ListRelease NotesVendor Advisory

Source: cverecord

https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc

Vendor Advisory

Source: cverecord

https://pkg.go.dev/vuln/GO-2026-5856

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUMCISA-ADP

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: LOW
Integrity: NONE
Availability: NONE

Vector?

Quick Info

StatusANALYZED

CWE

CWE-201

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