Vulnerability · Published Jul 8, 2026 · Assigned by Go
CVE-2026-42505Invoking Encrypted Client Hello privacy leak in crypto/tls
Medium 5.3
In plain English
A medium-severity security flaw in crypto/tls from Go standard library. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 32% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)0.4%top 67.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:8 | delve | 1.26.1-1.module_el8.10.0+4223+bd807c2e | ALSA-2026:38995 |
| AlmaLinux:9 | git-lfs | 3.7.1-4.el9_8.3 | ALSA-2026:66364 |
| AlmaLinux:10 | go-toolset | 1.26.5-1.el10_2.alma.1 | ALSA-2026:37436 |
| AlmaLinux:8 | go-toolset | 1.26.5-1.module_el8.10.0+4223+bd807c2e | ALSA-2026:38995 |
| AlmaLinux:9 | go-toolset | 1.26.5-1.el9_8 | ALSA-2026:37435 |
| AlmaLinux:10 | golang | 1.26.5-1.el10_2.alma.1 | ALSA-2026:37436 |
| AlmaLinux:8 | golang | 1.26.5-1.module_el8.10.0+4223+bd807c2e | ALSA-2026:38995 |
| AlmaLinux:9 | golang | 1.26.5-1.el9_8 | ALSA-2026:37435 |
| AlmaLinux:10 | golang-bin | 1.26.5-1.el10_2.alma.1 | ALSA-2026:37436 |
| AlmaLinux:8 | golang-bin | 1.26.5-1.module_el8.10.0+4223+bd807c2e | ALSA-2026:38995 |
| AlmaLinux:9 | golang-bin | 1.26.5-1.el9_8 | ALSA-2026:37435 |
| AlmaLinux:10 | golang-docs | 1.26.5-1.el10_2.alma.1 | ALSA-2026:37436 |
| AlmaLinux:8 | golang-docs | 1.26.5-1.module_el8.10.0+4223+bd807c2e | ALSA-2026:38995 |
| AlmaLinux:9 | golang-docs | 1.26.5-1.el9_8 | ALSA-2026:37435 |
| AlmaLinux:10 | golang-misc | 1.26.5-1.el10_2.alma.1 | ALSA-2026:37436 |
| AlmaLinux:8 | golang-misc | 1.26.5-1.module_el8.10.0+4223+bd807c2e | ALSA-2026:38995 |
| AlmaLinux:9 | golang-misc | 1.26.5-1.el9_8 | ALSA-2026:37435 |
| AlmaLinux:10 | golang-race | 1.26.5-1.el10_2.alma.1 | ALSA-2026:37436 |
| AlmaLinux:8 | golang-race | 1.26.5-1.module_el8.10.0+4223+bd807c2e | ALSA-2026:38995 |
| AlmaLinux:9 | golang-race | 1.26.5-1.el9_8 | ALSA-2026:37435 |
| AlmaLinux:10 | golang-src | 1.26.5-1.el10_2.alma.1 | ALSA-2026:37436 |
| AlmaLinux:8 | golang-src | 1.26.5-1.module_el8.10.0+4223+bd807c2e | ALSA-2026:38995 |
| AlmaLinux:9 | golang-src | 1.26.5-1.el9_8 | ALSA-2026:37435 |
| AlmaLinux:10 | golang-tests | 1.26.5-1.el10_2.alma.1 | ALSA-2026:37436 |
| AlmaLinux:8 | golang-tests | 1.26.5-1.module_el8.10.0+4223+bd807c2e | ALSA-2026:38995 |
| AlmaLinux:9 | golang-tests | 1.26.5-1.el9_8 | ALSA-2026:37435 |
| Alpine:v3.24 | go | 1.26.8-r0 | ALPINE-CVE-2026-42505 |
| Debian:13 | golang-1.24 | no fix listed | DEBIAN-CVE-2026-42505 |
| Debian:14 | golang-1.26 | 1.26.5-1 | DEBIAN-CVE-2026-42505 |
| Debian:14 | golang-1.27 | 1.27~rc2-1 | DEBIAN-CVE-2026-42505 |
| Go | stdlib | 1.25.12, 1.26.5, 1.27.0-rc.2 | GO-2026-5856 |
| Ubuntu:22.04:LTS | golang-1.17 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:22.04:LTS | golang-1.18 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:22.04:LTS | golang-1.20 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:22.04:LTS | golang-1.21 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:24.04:LTS | golang-1.21 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:22.04:LTS | golang-1.22 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:24.04:LTS | golang-1.22 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:22.04:LTS | golang-1.23 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:24.04:LTS | golang-1.23 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:25.10 | golang-1.23 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:26.04:LTS | golang-1.23 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:22.04:LTS | golang-1.24 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:24.04:LTS | golang-1.24 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:25.10 | golang-1.24 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:26.04:LTS | golang-1.24 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:22.04:LTS | golang-1.25 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:24.04:LTS | golang-1.25 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:25.10 | golang-1.25 | no fix listed | UBUNTU-CVE-2026-42505 |
| Ubuntu:26.04:LTS | golang-1.25 | no fix listed | UBUNTU-CVE-2026-42505 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Go standard library | crypto/tls | 0 – before 1.25.121.26.0-0 – before 1.26.51.27.0-0 – before 1.27.0-rc.2 |
Weakness: CWE-201 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N