Go standard library crypto-tls up to 1.25.11/1.26.4 TLS Handshake insertion of sensitive information into sent data

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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5.1$0-$5k1.13

Summaryinfo

A vulnerability has been found in Go standard library crypto-tls up to 1.25.11/1.26.4 and classified as problematic. Affected is an unknown function of the component TLS Handshake. The manipulation leads to insertion of sensitive information into sent data. This vulnerability is referenced as CVE-2026-42505. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in Go standard library crypto-tls up to 1.25.11/1.26.4 and classified as problematic. This issue affects an unknown part of the component TLS Handshake. The manipulation with an unknown input leads to a insertion of sensitive information into sent data vulnerability. Using CWE to declare the problem leads to CWE-201. The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor. Impacted is confidentiality. The summary by CVE is:

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.

The identification of this vulnerability is CVE-2026-42505 since 04/28/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1592 for this issue.

The vulnerability scanner Nessus provides a plugin with the ID 325629 (Linux Distros Unpatched Vulnerability : CVE-2026-42505), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.25.12, 1.26.5 or 1.27.0-rc.2 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (325629). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

Vendor

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.1

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Insertion of sensitive information into sent data
CWE: CWE-201 / CWE-200 / CWE-284
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 325629
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-42505

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Upgrade: crypto-tls 1.25.12/1.26.5/1.27.0-rc.2

Timelineinfo

04/28/2026 CVE reserved
07/08/2026 +71 days Advisory disclosed
07/08/2026 +0 days VulDB entry created
07/08/2026 +0 days VulDB entry last update

Sourcesinfo

Status: Confirmed

CVE: CVE-2026-42505 (🔒)
GCVE (CVE): GCVE-0-2026-42505
GCVE (VulDB): GCVE-100-376925

Entryinfo

Created: 07/08/2026 18:47
Updated: 07/08/2026 20:38
Changes: 07/08/2026 18:47 (53), 07/08/2026 18:55 (2), 07/08/2026 20:38 (2)
Complete: 🔍
Cache ID: 216::103

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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