Critical

Cisco fixes vulnerability exploited to DoS its firewalls (CVE-2026-20349)

Help Net Security

August 13, 2026 at 7:30 AM

Actively Exploited

Overview

Cisco has reported a high-severity vulnerability, designated as CVE-2026-20349, that attackers are using to cause temporary disruptions in the operation of Cisco firewalls. This flaw has been recognized by the Cybersecurity and Infrastructure Security Agency (CISA) and is included in their catalog of known exploited vulnerabilities. US civilian federal agencies are required to address this issue by August 14, 2026. While Cisco's Product Security Incident Response Team (PSIRT) became aware of the active exploitation in August, specific details regarding the attacks have not been disclosed. The urgency for remediation highlights the potential risks to organizations relying on Cisco’s firewall products.

Key Takeaways

Active Exploitation: This vulnerability is being actively exploited by attackers. Immediate action is recommended.
Affected Systems: Cisco firewalls (specific models not detailed)
Action Required: US civilian federal agencies must remediate by August 14, 2026.
Timeline: Disclosed on October 2023

Original Article Summary

A high-severity vulnerability (CVE-2026-20349) is being leveraged by attackers to temporarily interrupt the operation of Cisco firewalls, the company has confirmed. The flaw has been added to CISA’s Known Exploited Vulnerabilities catalog and needs to be remediated by US civilian federal agencies by August 14, 2026. Details about the attacks are currently under wraps. Cisco only shared that its Product Security Incident Response Team (PSIRT) became aware of active exploitation of this vulnerability in August … More → The post Cisco fixes vulnerability exploited to DoS its firewalls (CVE-2026-20349) appeared first on Help Net Security.

Impact

Cisco firewalls (specific models not detailed)

Exploitation Status

This vulnerability is confirmed to be actively exploited by attackers in real-world attacks. Organizations should prioritize patching or implementing workarounds immediately.

Timeline

Disclosed on October 2023

Remediation

US civilian federal agencies must remediate by August 14, 2026. Cisco recommends applying any available patches or updates to affected firewall products as they become available.

Additional Information

This threat intelligence is aggregated from trusted cybersecurity sources. For the most up-to-date information, technical details, and official vendor guidance, please refer to the original article linked below.

Related Topics: This incident relates to CVE, Cisco, Vulnerability.

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