Known Exploited Vulnerability

CVE-2023-20269

Cisco Adaptive Security Appliance and Firepower Threat Defense Unauthorized Access Vulnerability

Ransomware campaign 3 public exploits Added 13 Sept 2023 Due 04 Oct 2023 · 1038 days ago

VendorCisco

ProductAdaptive Security Appliance and Firepower Threat Defense

WeaknessCWE-288

RansomwareKnown use

What the flaw is

Cisco Adaptive Security Appliance and Firepower Threat Defense contain an unauthorized access vulnerability that could allow an unauthenticated, remote attacker to conduct a brute force attack in an attempt to identify valid username and password combinations or establish a clientless SSL VPN session with an unauthorized user.

Description as published by CISA. We have not independently reproduced it.

What CISA requires

Apply mitigations per vendor instructions for group-lock and vpn-simultaneous-logins or discontinue use of the product for unsupported devices.

This deadline is binding on US federal civilian agencies under BOD 22-01. It is not a legal deadline for anyone else, but it is a useful urgency signal — CISA sets it by how actively the flaw is being used, not by CVSS.

Public exploit code

3 public repositories referencing this CVE have been catalogued on GitHub. Treat this as a strong signal to prioritise patching, not as a verified working exploit — many such repositories are scanners, write-ups or forks rather than functional code.

Vendor advisories

Primary sources

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CVE-2026-20316

Source: CISA KEV catalog · last verified August 6, 2026. Rebuilt automatically twice a day.