CVE-2026-4528
Published: 21 March 2026
Summary
CVE-2026-4528 is a medium-severity SSRF (CWE-918) vulnerability in Notion (inferred from references). Its CVSS base score is 6.9 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 18.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 AC-4 (Information Flow Enforcement) and SI-10 (Information Input Validation).
Deeper analysis
CVE-2026-4528 is a server-side request forgery (SSRF) vulnerability, classified under CWE-918, affecting trueleaf ApiFlow version 0.9.7. The flaw exists in the validateUrlSecurity function located in the file packages/server/src/service/proxy/http_proxy.service.ts within the URL Validation Handler component. Published on 2026-03-21, it carries a CVSS v3.1 base score of 7.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L), indicating high severity due to its network accessibility and low complexity.
Remote attackers can exploit this vulnerability without privileges or user interaction, enabling server-side request forgery. By manipulating the URL validation, attackers can trick the server into making unauthorized requests, potentially leading to limited impacts on confidentiality, integrity, and availability as per the CVSS vector.
Advisories available at VulDB (ctiid.352316, id.352316, submit.784197) and a Notion page detail the SSRF issue in ApiFlow, noting that the exploit has been publicly disclosed and may be utilized by attackers. Security practitioners should review these references for additional technical details and recommended mitigations.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14258
Vulnerability details
A vulnerability was determined in trueleaf ApiFlow 0.9.7. The impacted element is the function validateUrlSecurity of the file packages/server/src/service/proxy/http_proxy.service.ts of the component URL Validation Handler. This manipulation causes server-side request forgery. Remote exploitation of the attack is possible. The exploit…
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has been publicly disclosed and may be utilized.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
SSRF vuln in public-facing server app enables direct exploitation via T1190; SSRF responses commonly facilitate internal network/port scanning mapped to T1046.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly addresses the flawed validateUrlSecurity function by requiring validation of URL inputs to prevent malicious inputs from enabling server-side request forgery.
Enforces approved information flows in the http_proxy.service, blocking unauthorized server-initiated requests to attacker-controlled URLs.
Implements boundary protections such as proxies or firewalls to monitor and restrict outbound requests from the URL Validation Handler, mitigating SSRF exploitation.