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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.

PUBLISHED Reserved 2026-07-10 | Published 2026-07-14 | Updated 2026-07-14 | Assigner VulnCheck




MEDIUM: 6.3CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N

HIGH: 7.7CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Problem types

Server-Side Request Forgery (SSRF)

Product status

Default status
affected

2.1.0 (semver) before 2.1.7
affected

4bf35cf9e45573a5f55a6f52995086c1da89c096 (git)
unaffected

3.0.0 (semver)
unaffected

b4d23dfd74a511587c605f9d294cefc3a75b4b26 (git)
affected

Credits

Hamed Kohi finder

VulnCheck finder

References

github.com/...ommit/4bf35cf9e45573a5f55a6f52995086c1da89c096 (Patch Commit (v2.1)) patch

github.com/...ommit/b4d23dfd74a511587c605f9d294cefc3a75b4b26 (Patch Commit (v3.0)) patch

www.vulncheck.com/...ple-machines-forum-ssrf-via-image-proxy third-party-advisory

cve.org (CVE-2026-61520)

nvd.nist.gov (CVE-2026-61520)

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