How severe is CVE-2021-26598?

CVE-2021-26598 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-26598?

CVE-2021-26598 affects the following packages: impresscms/impresscms (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-26598?

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.

How do I detect CVE-2021-26598 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for impresscms/impresscms. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2021-26598 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2021-26598?

O3 pinpoints whether CVE-2021-26598 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2021-26598 actively exploited in the wild?

Yes. There are 4 known exploit references for CVE-2021-26598, including 4 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-26598?

CVE-2021-26598 has an EPSS (Exploit Prediction Scoring System) score of 10.8%, placing it in the 95th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

What type of vulnerability is CVE-2021-26598?

CVE-2021-26598 is classified as Improper Authentication (CWE-287). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Is there exploit tooling available for CVE-2021-26598?

A Nuclei detection template exists for CVE-2021-26598, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2021-26598 published, and has it been updated?

CVE-2021-26598 was published on March 28, 2022 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

CVE-2021-26598

MEDIUM

Incorrect Access Control in ImpressCMS

Also known asGHSA-48p3-xfvw-g59c

Published

Mar 28, 2022

Updated

Apr 10, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

4 known

EPSS Exploitation Probability

via FIRST.org ↗

10.8%probability of exploitation in next 30 days

Moderate Risk95th percentile-65.25%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

🐘impresscms/impresscms

Real-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

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`impresscms/impresscms`	all versions	1.4.3

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

ImpressCMS before 1.4.3 has Incorrect Access Control because include/fin…

karmainsecurity.comNVDApr 2022

ImpressCMS before 1.4.3 has Incorrect Access Control because include/fin…

hackerone.comNVDApr 2022

ImpressCMS before 1.4.3 has Incorrect Access Control because include/fin…

packetstormsecurity.comNVDApr 2022

ImpressCMS before 1.4.3 has Incorrect Access Control because include/fin…

seclists.orgNVDApr 2022

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for impresscms/impresscms. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2021-26598 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2021-26598. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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).

O3 Security · Impact-Aware SCA

Is CVE-2021-26598 in your dependencies?

O3 detects CVE-2021-26598 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works

CVE-2021-26598

EPSS Exploitation Probability

Blast Radius

Description

Affected Packages

Detection & mitigation playbook

Detect

Fix

Workarounds

How O3 protects you

Frequently Asked Questions

Is CVE-2021-26598 in your dependencies?