{"id":"CVE-2026-42505","title":"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.","summary":"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.","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","cwe":["CWE-201"],"vendor":"golang","product":"go","affected":["go >= 1.23.0, < 1.25.12","go >= 1.26.0, < 1.26.5","go = 1.27"],"patched":["go 1.26.5"],"published":"2026-07-08","updated":"2026-09-16","sourceUpdated":"2026-09-16T20:14:44.473","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-42505","references":[{"url":"https://go.dev/cl/775960","label":"security@golang.org"},{"url":"https://go.dev/issue/79282","label":"security@golang.org"},{"url":"https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc","label":"security@golang.org"},{"url":"https://pkg.go.dev/vuln/GO-2026-5856","label":"security@golang.org"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42505.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-42505"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2498138"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-42505"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-42505"},{"url":"https://access.redhat.com/errata/RHSA-2026:37436"},{"url":"https://access.redhat.com/errata/RHSA-2026:38995"},{"url":"https://access.redhat.com/errata/RHSA-2026:37435"},{"url":"https://access.redhat.com/errata/RHSA-2026:36510"},{"url":"https://access.redhat.com/errata/RHSA-2026:36477"},{"url":"https://access.redhat.com/errata/RHSA-2026:54773"}],"tags":["nvd","csaf","vex","red-hat","osv","go"],"epss":0.00382,"epssPercentile":0.32001,"aliases":["GO-2026-5856"],"ecosystem":"go","ingestedAt":"2026-07-09T18:56:37.250Z","slug":"CVE-2026-42505","body":"## Overview\n\nHandshakes 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.\n\n## Affected\n\n- `go >= 1.23.0, < 1.25.12`\n- `go >= 1.26.0, < 1.26.5`\n- `go = 1.27`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `go 1.26.5`\n\n## Package advisory (CVE-2026-42505)\n\nAffected packages:\n\n- `stdlib >= 1.27.0-0, < 1.27.0-rc.2`\n\nPatched in:\n\n- `stdlib 1.27.0-rc.2`\n\nSource: https://osv.dev/vulnerability/GO-2026-5856\n\n## Vendor advisories\n\n- **RHSA-2026:37436** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10) · released 2026-07-09 · [advisory](https://access.redhat.com/errata/RHSA-2026:37436)\n- **RHSA-2026:38995** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 8) · released 2026-07-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:38995)\n- **RHSA-2026:37435** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9) · released 2026-07-09 · [advisory](https://access.redhat.com/errata/RHSA-2026:37435)\n- **RHSA-2026:36510** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-07-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:36510)\n- **RHSA-2026:36477** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-07-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:36477)\n- **RHSA-2026:54773** · Red Hat · fixed in: Red Hat OpenShift distributed tracing 3.10.2 · released 2026-08-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:54773)\n- **Red Hat VEX** · Moderate · affected: Assisted Installer for Red Hat OpenShift Container Platform 2, Builds for Red Hat OpenShift, cert-manager Operator for Red Hat OpenShift, Compliance Operator, Confidential Compute Attestation, Cryostat 4, … · no fix planned: Assisted Installer for Red Hat OpenShift Container Platform 2, Builds for Red Hat OpenShift, cert-manager Operator for Red Hat OpenShift, Compliance Operator, … · updated 2026-09-08 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42505.json)","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":5202,"id":"CVE-2026-42505","ts":1788887253533,"field":"cvss","old":null,"new":"5.3"},{"seq":5201,"id":"CVE-2026-42505","ts":1788887253533,"field":"severity","old":"none","new":"medium"},{"seq":4085,"id":"CVE-2026-42505","ts":1788886369383,"field":"cvss","old":"5.3","new":null},{"seq":4084,"id":"CVE-2026-42505","ts":1788886369383,"field":"severity","old":"medium","new":"none"},{"seq":3151,"id":"CVE-2026-42505","ts":1788883133067,"field":"cvss","old":null,"new":"5.3"},{"seq":3150,"id":"CVE-2026-42505","ts":1788883133067,"field":"severity","old":"none","new":"medium"}]}