Cyber Resilience

CVE-2026-39521

SSRF

SSRF
Published
08 April 2026
Modified
24 July 2026
CVSS Score v3.1 4.9
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:N
EPSS Score 0.0014 4th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-39521 is a medium-severity SSRF (CWE-918) vulnerability. Its CVSS base score is 4.9 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to AC-4 (Information Flow Enforcement) and SC-7 (Boundary Protection) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A01:2025 Broken Access Control

EU & UK References

Vulnerability Data

Server-Side Request Forgery (SSRF) vulnerability in Nelio Software Nelio Content nelio-content allows Server Side Request Forgery.This issue affects Nelio Content: from n/a through <= 4.3.1.

CWE(s)
CWE-918

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Why these techniques?

SSRF in public-facing WordPress plugin directly enables initial exploitation of the application.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2025-64663Shared CWE-918
CVE-2026-27023Shared CWE-918
CVE-2026-0932Shared CWE-918
CVE-2026-41688Shared CWE-918
CVE-2026-3683Shared CWE-918
CVE-2026-1313Shared CWE-918
CVE-2026-49328Shared CWE-918
CVE-2026-2532Shared CWE-918
CVE-2026-6981Shared CWE-918
CVE-2026-24231Shared CWE-918

Affected Assets

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • AC-4 Information Flow Enforcement
  • SC-7 Boundary Protection
  • SI-10 Information Input Validation
Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.3.6
  • V1.5.3
  • V5.3.2
  • V10.4.7

Mitigating Controls (NIST 800-53 r5) AI

AC-4 Information Flow Enforcement good match
prevent

Enforces information flow policies that block the plugin from issuing server-side requests to arbitrary or internal destinations.

SC-7 Boundary Protection good match
prevent

Restricts outbound network connections from the web server, preventing SSRF requests to internal resources or external targets.

SI-10 Information Input Validation good match
prevent

Validates and sanitizes URL inputs supplied to Nelio Content features, rejecting malicious payloads that trigger SSRF.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure development practices directly include input validation and destination allow-listing that prevent SSRF.

DE.CM-09 partial match
prevents

Runtime monitoring of web applications and services can detect anomalous outbound requests indicative of SSRF.

ID.RA-01 partial match
prevents

Vulnerability identification processes can discover and record SSRF flaws in web applications.

PR.IR-01 partial match
prevents

Network segmentation and egress controls can limit the damage from successful SSRF requests.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.7 Threat intelligence partial match
prevents

Operational threat data describing SSRF campaigns can be used to tighten outbound-request allow-lists and detection rules before attackers exploit them.

References