CVE-2026-28281

HighPublic PoC

Published: 10 March 2026

Published

10 March 2026

Modified

13 March 2026

KEV Added

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Patch

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CVSS Score v3.1 7.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N

EPSS Score 0.0003 8.3th percentile

Risk Priority 14 60% EPSS · 20% KEV · 20% CVSS

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 8.3th 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 are NIST 800-53 AC-3 (Access Enforcement) and SI-10 (Information Input Validation).

Deeper analysis

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.

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-10405

Vulnerability details

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…

of the user. This vulnerability is fixed in 2.18.1.

CWE(s): CWE-352

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 →

T1566.002 Spearphishing Link Initial Access

Adversaries may send spearphishing emails with a malicious link in an attempt to gain access to victim systems.

attack.mitre.org →

T1204.001 Malicious Link Execution

An adversary may rely upon a user clicking a malicious link in order to gain execution.

attack.mitre.org →

T1098 Account Manipulation Persistence

Adversaries may manipulate accounts to maintain and/or elevate access to victim systems.

attack.mitre.org →

Why these techniques?

CSRF in public-facing CMS directly enables remote exploitation of the web app (T1190) delivered via attacker-crafted links/pages requiring user interaction (T1566.002, T1204.001); successful abuse permits unauthorized account changes such as privilege grants (T1098).

Confidence: MEDIUM · MITRE ATT&CK Enterprise v18.1