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CVE-2025-59055: InstantCMS vulnerable to Server-Side Request Forgery via package installer

• Severity: high (CVSS 7.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-09-11 · updated 2026-06-17
• Weakness: CWE-918

Description

InstantCMS is a free and open source content management system. A blind Server-Side Request Forgery (SSRF) vulnerability in InstantCMS up to and including 2.17.3 allows authenticated remote attackers to make nay HTTP/HTTPS request via the package parameter. It is possible to make any HTTP/HTTPS request to any website in installer functionality. Due to such vulnerability it is possible to for example scan local network, call local services and its functions, conduct a DoS attack, and/or disclose a server's real IP if it's behind a reverse proxy. It is also possible to exhaust server resources by sending plethora of such requests. As of time of publication, no patched releases are available.

Affected products

• InstantCMS: through 2.17.3

References

• https://github.com/instantsoft/icms2/commit/fa997bdab3429fad0c850966bfacbcb96d5ab041
• https://github.com/instantsoft/icms2/security/advisories/GHSA-79hh-mhvg-whrw

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