CVE-2026-49979
Received Received - Intake
Email Server Connection Bypass in Appsmith

Publication date: 2026-06-24

Last updated on: 2026-06-24

Assigner: GitHub, Inc.

Description
Appsmith is a platform to build admin panels, internal tools, and dashboards. Prior to 1.99, the POST /api/v1/admin/send-test-email endpoint accepts attacker-controlled smtpHost and smtpPort values and establishes a raw JavaMail TCP connection without any IP validation. This completely bypasses WebClientUtils.IP_CHECK_FILTER, which only applies to Spring WebClient HTTP requests. Additionally, the raw MailException.getMessage() is returned verbatim in the API error response, enabling error-based internal port scanning and service banner enumeration. This vulnerability is fixed in 1.99.
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Meta Information
Published
2026-06-24
Last Modified
2026-06-24
Generated
2026-06-25
AI Q&A
2026-06-25
EPSS Evaluated
N/A
NVD
CVE-2026-49979
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
appsmith appsmith to 1.99 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-918 The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
CWE-209 The product generates an error message that includes sensitive information about its environment, users, or associated data.
Attack-Flow Graph
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Executive Summary

This vulnerability exists in Appsmith versions prior to 1.99 in the POST /api/v1/admin/send-test-email endpoint. The endpoint accepts attacker-controlled smtpHost and smtpPort values and establishes a raw JavaMail TCP connection without validating the IP address. This bypasses the WebClientUtils.IP_CHECK_FILTER, which only applies to Spring WebClient HTTP requests, not raw TCP connections.

Additionally, the raw error message from MailException.getMessage() is returned directly in the API error response. This behavior allows attackers to perform error-based internal port scanning and service banner enumeration.

The vulnerability is fixed in Appsmith version 1.99.

Impact Analysis

An attacker can exploit this vulnerability to bypass IP validation controls and establish unauthorized TCP connections to internal services using the smtpHost and smtpPort parameters.

By receiving raw error messages, the attacker can perform internal port scanning and enumerate service banners, potentially revealing sensitive information about internal network services.

This can lead to increased risk of further attacks targeting internal infrastructure that is otherwise protected by IP filtering.

Mitigation Strategies

The vulnerability is fixed in Appsmith version 1.99. Immediate mitigation involves upgrading your Appsmith installation to version 1.99 or later.

Since the vulnerability involves the POST /api/v1/admin/send-test-email endpoint accepting attacker-controlled smtpHost and smtpPort values without IP validation, restricting access to this endpoint and monitoring for suspicious usage may help reduce risk until the upgrade is applied.

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