Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:NCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-28281 is a high-severity CSRF (CWE-352) vulnerability in Instantcms Instantcms. Its CVSS base score is 7.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and SC-23 (Session Authenticity) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-28281 is a Cross-Site Request Forgery (CSRF) vulnerability, classified under CWE-352, affecting InstantCMS, a free and open source content management system. In versions prior to 2.18.1, the software fails to validate CSRF tokens, enabling unauthorized actions when a victim is tricked into performing a state-changing operation. The vulnerability carries a CVSS v3.1 base score of 7.1 (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N), indicating network accessibility, low attack complexity, no privileges required, user interaction needed, low confidentiality impact, high integrity impact, and no availability impact.
Unauthenticated attackers can exploit this remotely by crafting malicious web pages or links that, when visited by an authenticated InstantCMS user, trigger forged requests lacking valid CSRF tokens. This allows attackers to perform actions on the victim's behalf, such as granting moderator privileges to arbitrary users, executing scheduled tasks, moving posts to trash, and accepting friend requests.
The vulnerability is addressed in InstantCMS version 2.18.1, which implements proper CSRF token validation. Additional details on the issue and patch are available in the GitHub security advisory at https://github.com/instantsoft/icms2/security/advisories/GHSA-pp43-262q-h73m.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-10405
Vulnerability Data
InstantCMS is a free and open source content management system. Prior to 2.18.1, InstantCMS does not validate CSRF tokens, which allows attackers grant moderator privileges to users, execute scheduled tasks, move posts to trash, and accept friend requests on behalf…
more
of the user. This vulnerability is fixed in 2.18.1.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V3.3.2V3.5.1V10.2.1
Mitigating Controls (NIST 800-53 r5) AI
Access enforcement requires verifying that state-changing requests originate from the authenticated user rather than a forged cross-site source.
Protecting session authenticity prevents attackers from replaying or forging authenticated requests via the victim's browser.
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.
Secure SDLC practices directly require anti-CSRF controls such as tokens or SameSite attributes.
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.
By denying access to phishing or malicious sites, the control lowers the likelihood that a user will be tricked into submitting a forged request that performs an unintended action on another site.