CVE-2026-61520

Deferred Deferred - Pending Action

Server-Side Request Forgery in Simple Machines Forum

Publication date: 2026-07-14

Last updated on: 2026-07-15

Assigner: VulnCheck

Description

Simple Machines Forum 2.1 prior to commit 4bf35cf and 3.0 prior to commit b4d23df contains a server-side request forgery vulnerability in the image proxy that allows authenticated attackers to trigger internal HTTP requests by embedding attacker-controlled URLs in BBCode image tags, which the proxy fetches without validating resolved destination IPs against private address ranges, loopback, or link-local addresses. Attackers can leverage SMF's automatic HMAC signature generation for any embedded image URL to obtain valid signed proxy requests targeting internal services such as cloud instance metadata endpoints, internal web applications, and container network services.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-07-14

Last Modified

2026-07-15

Generated

2026-08-04

AI Q&A

2026-07-15

EPSS Evaluated

2026-08-02

NVD

CVE-2026-61520

Affected Vendors & Products

Vendor	Product	Version / Range
simple_machines_forum	simple_machines_forum	to 3.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

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.

Attack-Flow Graph

Executive Summary

This vulnerability affects Simple Machines Forum (SMF) versions before commit 4bf35cf (2.1) and b4d23df (3.0). It is a server-side request forgery (SSRF) issue in the image proxy feature. Authenticated attackers can embed malicious URLs in BBCode image tags, which SMF fetches without validating the destination IP addresses. This allows attackers to make internal HTTP requests to private, loopback, or link-local addresses, potentially targeting internal services like cloud metadata endpoints or container networks.

Detection Guidance

Detecting this SSRF vulnerability in Simple Machines Forum requires checking for improperly handled image proxy requests. Monitor network logs for outbound HTTP requests to private, loopback, or link-local IP ranges originating from the SMF application. Inspect BBCode image tags in posts for URLs pointing to internal services or metadata endpoints. Check for unusual signed proxy requests to cloud instance metadata services like AWS, Azure, or GCP.

Impact Analysis

If you use a vulnerable SMF version, attackers could exploit this to access internal services on your network. This might lead to unauthorized data exposure, service disruption, or further attacks against internal systems. The impact depends on your network configuration and what internal services are accessible.

Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by enabling unauthorized access to internal systems through SSRF. Attackers could exploit it to interact with internal services, potentially accessing or exfiltrating sensitive data, which violates data protection requirements under these regulations.

Mitigation Strategies

Upgrade Simple Machines Forum to versions 2.1 commit 4bf35cf or later and 3.0 commit b4d23df or later to address the SSRF vulnerability in the image proxy.

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