axllent mailpit up to 1.28.2 HTML Check Feature html-check inlineRemoteCSS server-side request forgery

CVSS Meta Temp Score
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CTI Interest Score
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6.8$0-$5k0.00

Summaryinfo

A vulnerability was found in axllent mailpit up to 1.28.2. It has been declared as critical. This vulnerability affects the function inlineRemoteCSS of the file /api/v1/message/{ID}/html-check of the component HTML Check Feature. Executing a manipulation can lead to server-side request forgery. This vulnerability is tracked as CVE-2026-23845. The attack can be launched remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in axllent mailpit up to 1.28.2. It has been declared as critical. This vulnerability affects the function inlineRemoteCSS of the file /api/v1/message/{ID}/html-check of the component HTML Check Feature. The manipulation with an unknown input leads to a server-side request forgery vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Mailpit is an email testing tool and API for developers. Versions prior to 1.28.3 are vulnerable to Server-Side Request Forgery (SSRF) via HTML Check CSS Download. The HTML Check feature (`/api/v1/message/{ID}/html-check`) is designed to analyze HTML emails for compatibility. During this process, the `inlineRemoteCSS()` function automatically downloads CSS files from external `<link rel="stylesheet" href="...">` tags to inline them for testing. Version 1.28.3 fixes the issue.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-23845 since 01/16/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available.

Upgrading to version 1.28.3 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 1679a0aba592ebc8487a996d37fea8318c984dfe is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at EUVD (EUVD-2026-3296) and CERT Bund (WID-SEC-2026-0146). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

  • Open Source MailPit

Productinfo

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.9
VulDB Meta Temp Score: 6.8

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 7.5
NVD Vector: 🔒

CNA Base Score: 5.8
CNA Vector (GitHub_M): 🔒

CVSSv2info

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

Exploitinginfo

Class: Server-side request forgery
CWE: CWE-918
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: mailpit 1.28.3
Patch: 1679a0aba592ebc8487a996d37fea8318c984dfe

Timelineinfo

01/16/2026 CVE reserved
01/19/2026 +3 days VulDB entry created
01/20/2026 +0 days Advisory disclosed
02/05/2026 +16 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: GHSA-6jxm-fv7w-rw5j
Status: Confirmed

CVE: CVE-2026-23845 (🔒)
GCVE (CVE): GCVE-0-2026-23845
GCVE (VulDB): GCVE-100-341872
EUVD: 🔒
CERT Bund: WID-SEC-2026-0146 - MailPit: Mehrere Schwachstellen

Entryinfo

Created: 01/20/2026 00:10
Updated: 02/05/2026 21:09
Changes: 01/20/2026 00:10 (70), 01/20/2026 00:50 (1), 01/20/2026 05:17 (1), 01/20/2026 11:51 (7), 02/05/2026 21:09 (11)
Complete: 🔍
Cache ID: 216::103

VulDB is the best source for vulnerability data and more expert information about this specific topic.

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