Which versions of Language Servers for AWS are affected by CVE-2026-12957?

AWS Language Servers is vulnerable to arbitrary code execution when developers open malicious workspace configurations, creating direct risk to source code integrity, intellectual property theft, and…. A patch is available.

Is there a public PoC exploit available for CVE-2026-12957?

Yes, a public proof-of-concept exploit is available for CVE-2026-12957. Prioritise patching immediately. EPSS: 0.1%.

How to fix or mitigate CVE-2026-12957?

Immediately (24 hours): Inventory all development systems running AWS Language Servers and disable automatic workspace trust functionality; require explicit security approval before opening any external projects. Within 7 days: Review AWS security advisories for patch availability and establish version control policy for Language Server deployments. Within 30 days: Conduct code audit of projects accessed in potentially compromised environments and deliver developer security training on workspace trust threats.

Language Servers for AWS CVE-2026-12957

Q: What is the CVSS score of CVE-2026-12957?

CVE-2026-12957 has a CVSS 4.0 base score of 8.5 (High). CVSS vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.1%.

EUVD-2026-38488 HIGH

Incorrect Permission Assignment for Critical Resource (CWE-732)

2026-06-23 AMZN

RCE Language Servers For Aws

8.5

CVSS 4.0 · Vendor: AMZN

Severity by source

Vendor (AMZN) PRIMARY

8.5 HIGH

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

vuln.today AI

7.8 HIGH

Local workspace delivery (AV:L), no auth needed against the language server (PR:N), but victim must actively accept trust prompt (UI:R); full host code execution yields C/I/A:H.

3.1 AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

4.0 AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (AMZN).

CVSS VectorVendor: AMZN

Attack Vector

Local

Attack Complexity

Low

Privileges Required

None

User Interaction

Scope

Lifecycle Timeline

Patch available

Jun 23, 2026 - 18:17 EUVD

Analysis Generated

Jun 23, 2026 - 17:00 vuln.today

DescriptionCVE.org

Improper trust boundary enforcement in Language Servers for AWS before version 1.65.0 on all supported platforms may allow a for arbitrary code execution. If a local user opens a maliciously crafted workspace, any commands within the project configuration files may be automatically executed. This issue requires the user to trust the workspace when prompted.

To remediate this issue, users should upgrade to Language Servers for AWS version 1.65.0 or higher.

Articles & Coverage 1

synthex.medium.com CVE-2026-12957: Zero-Click RCE via AWS Language Server Protocol Integration Jun 27, 2026

AnalysisAI

Arbitrary code execution in AWS Language Servers prior to version 1.65.0 allows attackers to run commands on a developer's machine when a victim opens and trusts a maliciously crafted workspace. The flaw stems from improper trust boundary enforcement (CWE-732) that causes commands embedded in project configuration files to execute automatically. No public exploit identified at time of analysis, but the requirement for only passive user interaction (workspace trust prompt) makes this a credible developer-targeting threat.

Technical ContextAI

Language Servers for AWS implement the Language Server Protocol (LSP) used by AWS-integrated IDE tooling (such as the AWS Toolkit / Q Developer extensions) to provide code intelligence - completion, linting, diagnostics - for AWS-flavored project files. CWE-732 (Incorrect Permission Assignment for Critical Resource) here manifests as a broken trust boundary: configuration directives that should be inert data are instead handed to a command executor when the language server initializes the workspace. The CPE 'cpe:2.3:a:amazon_web_services:language_servers_for_aws:*' covers all versions of the component prior to 1.65.0 across all supported platforms (Windows, macOS, Linux IDE hosts).

RemediationAI

Vendor-released patch: Language Servers for AWS 1.65.0 - upgrade to this version or later, which is the primary fix per the AWS security bulletin at https://aws.amazon.com/security/security-bulletins/2026-047-aws/. For IDE extension users, update the AWS-related extension (AWS Toolkit, Amazon Q Developer, etc.) so it pulls in the patched language server. Until patched, the actionable workaround is to never accept the 'Trust this workspace' prompt for repositories obtained from untrusted sources, and to inspect project configuration files in a plain text editor before opening folders in an IDE that loads AWS language servers - the side effect is loss of full IntelliSense/diagnostics for untrusted projects, which is preferable to silent code execution.