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VulnerabilityPublished Updated

CVE-2026-20349: Cisco Secure Firewall Adaptive Security Appliance (ASA) Software · Heap Inspection

Affects Cisco Secure Firewall Adaptive Security Appliance (ASA) SoftwareSource CVE Database V5

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Exploited in the wild · KEV due 14 Aug 2026 · 1% EPSS : apply the vendor's fix or mitigations to Cisco Secure Firewall Adaptive Security Appliance (ASA) Software now.

Data as of 9 Nov 2026, 23:24 UTC

CVSS 3.1 base score
8.6High
How severe the flaw is on the 0–10 CVSS scale.
KEV deadline
 US federal agencies must patch by this date; a sensible deadline for everyone else. Other KEV due dates
EPSS
1.0% chance of exploitation in 30 days – higher than 63% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

  1. Disclosed: evidence found.

    CVE published 11 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    Public exploit code: GitHub proofs of concept

  4. Exploited in the wild: evidence found.

    Listed in CISA KEV the same day as disclosure

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by Cisco Systems, Inc.

    , 307 days before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. In Threat Radar

    record ingested

    , 6 minutes after disclosure

  4. , the same day as disclosure

  5. KEV remediation due

    US federal deadline

    , 3 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), GitHub proofs of concept, CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Affected software

ProductAffectedFixed in
CiscoCisco Secure Firewall Adaptive Security Appliance (ASA) SoftwareAffected
  • 9.16.1 – 9.24.1.155
132 affected builds
Fixed in–
CiscoCisco Secure Firewall Threat Defense (FTD) SoftwareAffected
  • 7.0.0 – 10.0.2
61 affected builds
Fixed in–

Check the firmware or software version for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software in the device's admin interface against the vendor advisory.

Description

A vulnerability in the Remote Access SSL VPN service for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition.  This vulnerability is due to insufficient error checking when processing HTTP requests. An attacker could exploit this vulnerability by sending a crafted HTTP request to the Remote Access SSL VPN service on an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.

References

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