CVE-2021-26598 is a medium-severity (CVSS 5.3) Improper Authentication vulnerability in impresscms/impresscms. 4 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for impresscms/impresscms — see the affected versions and patch details below.
Incorrect Access Control in ImpressCMS
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
impresscms/impresscmsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
ImpressCMS before 1.4.3 has Incorrect Access Control because include/findusers.php allows access by unauthenticated attackers (who are, by design, able to have a security token).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | impresscms/impresscms | all versions | 1.4.3composer require impresscms/impresscms:^1.4.3 |
Affected Products
impresscmsimpresscmsResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for impresscms/impresscms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update impresscms/impresscms to 1.4.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-26598 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
How to detect CVE-2021-26598
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2021-26598 -u https://target- Template
- ImpressCMS <1.4.3 - Incorrect Authorization
- Severity
- medium
- Impact
- An attacker can bypass authorization and gain unauthorized access to sensitive information or perform unauthorized actions.
- Remediation
- Upgrade to ImpressCMS version 1.4.3 or later to fix the vulnerability.
Template by ProjectDiscovery nuclei-templates (gy741, pdteam), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2021-26598 in your dependencies?
Find it across Packagist, including transitive dependencies.