How severe is CVE-2023-28771?

CVE-2023-28771 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2023-28771?

Affected package information for CVE-2023-28771 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2023-28771?

No patched version of the affected component has shipped for CVE-2023-28771 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

How do I detect CVE-2023-28771 in my code and dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. 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-2023-28771 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-2023-28771?

O3 pinpoints whether CVE-2023-28771 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-2023-28771 actively exploited in the wild?

Yes. There are 9 known exploit references for CVE-2023-28771, including 8 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-2023-28771?

CVE-2023-28771 has an EPSS (Exploit Prediction Scoring System) score of 99.3%, placing it in the 100th 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. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2023-28771 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2023-28771 (Zyxel Multiple Firewalls OS Command Injection Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2023-05-31. CISA required all US federal civilian agencies to remediate this vulnerability by 2023-06-21. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2023-28771?

CVE-2023-28771 is classified as OS Command Injection (CWE-78). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2023-28771 published, and has it been updated?

CVE-2023-28771 was published on April 25, 2023 and was last updated on October 21, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2023-05-31 — agencies required to remediate by 2023-06-21

CVE-2023-28771

CRITICAL

Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60…

Published

Apr 25, 2023

Updated

Oct 21, 2025

Affected

0 pkgs

Patched

None yet

Exploits

9 known

EPSS Exploitation Probability

via FIRST.org ↗

99.3%probability of exploitation in next 30 days

Very High Risk100th percentile0.00%

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.

Description

Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.

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.