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Highest advisory severityMedium 1 vendor · 1 advisory

CVE-2026-20248

CVE-2026-20248: 1 tracked advisory record across Cisco. Compare vendor sources and published fix guidance.

Compare the source-linked records below. Ratings and product/version details belong to each advisory; they are not a single CVE-wide score or proof that every listed product is affected. How VulniPulse collects and checks evidence.

NVD detail CVE.org

Vendor advisory comparison

Cisco

1 advisory
  • Advisory severityMedium6.8

    Medium [CVE-2026-20248] Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software TCP DNS Denial of Service Vulnerability

    cisco-sa-asaftd-tcpdns-dos-p6dUnjr5Source published Source updated

    A vulnerability in the DNS over TCP implementation of 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 TCP DNS response handler to unexpectedly restart, causing the device to reload. This vulnerability is due to a logic error when parsing a DNS query and tracking the size of the incoming buffers. An attacker could exploit this vulnerability by formatting a crafted reply to a DNS query sent from the targeted device. A successful exploit could allow the attacker to cause the device to reload, causing a denial of service (DoS) condition. Note: The attacker must be able to respond to DNS queries from the device, either by controlling the DNS service or through…

    Affected products in this advisory
    • Secure Firewall Adaptive Security Appliance (ASA) Software
    • Firepower 2100 Series
    • Firepower 1000 Series
    • ASA 5500-X Series Firewalls

    4 more entries in the full advisory.

    Source-reported affected versions
    • Scope: At the time of publication, this vulnerability affected Cisco Secure Firewall ASA Software and Secure FTD Software, regardless of device configuration.
    • Release N/A (first fixed: 9.16 and earlier / 9.18)
    • Release 9.18.4.94 (first fixed: 9.18.4.135 / 9.20.4.235)
    • Release 9.22 (first fixed: 9.20.4.49 / 9.22.3.26)

    9 more entries in the full advisory.

    Source-reported fixed versions
    • 9.16 and earlier / 9.18
    • 9.18.4.135 / 9.20.4.235
    • 9.20.4.49 / 9.22.3.26
    • 9.23 / 9.23.1.47

    8 more entries in the full advisory.

    Mitigation guidance
    • Upgrade to the first fixed release for your train per the Fixed Releases table in this advisory.
    • Release N/A: upgrade to 9.16 and earlier / 9.18.
    • Release 9.18.4.94: upgrade to 9.18.4.135 / 9.20.4.235.
    • Release 9.22: upgrade to 9.20.4.49 / 9.22.3.26.

    5 more entries in the full advisory.

    Workarounds
    • There are no workarounds that address this vulnerability.
    Full advisory and evidenceOpen source bulletin

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