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major vulnerability· requires attention

Widely deployed Cisco ASA/FTD; DoS could disrupt remote access for many organizations.

Networks

CVE-2026-20103

8.6
High
EPSS 0.35%Patch availableMar 5, 2026

DoS via crafted packets to Cisco SSL VPN causing memory exhaustion and service unavailability.

common questions

Is CVE-2026-20103 being exploited?

Not confirmed. CVE-2026-20103 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.35% probability of exploitation in the next 30 days.

How severe is CVE-2026-20103?

CVE-2026-20103 is rated High with a CVSS score of 8.6. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2026-20103?

Yes. A fix has been recorded for CVE-2026-20103. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2026-20103 affect?

CVE-2026-20103 affects Cisco Secure Firewall ASA, Cisco Secure Firewall Threat Defense (FTD). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

What should I do about CVE-2026-20103?

Plan upgrade to patched ASA/FTD when available; monitor SSL VPN traffic.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

executive summary
technical analysis
affected
Cisco Secure Firewall ASACisco Secure Firewall Threat Defense (FTD)
impact

Unauthenticated attacker can exhaust SSL VPN memory via crafted packets, causing remote access and web UI to become unresponsive.

action required

Monitor only

affected versions
Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
  • affected9.12.4.48
  • affected9.12.4.50
  • affected9.12.4.52
  • affected9.12.4.54
  • affected9.12.4.55
  • affected9.12.4.56
  • affected9.12.4.58
  • affected9.12.4.62
  • affected9.12.4.65
  • affected9.12.4.67
  • affected9.16.3.15
  • affected9.16.3.19
  • affected9.16.3.23
  • affected9.16.4
  • affected9.16.4.9
  • affected9.16.4.14
  • affected9.16.4.19
  • affected9.16.4.27
  • affected9.16.4.38
  • affected9.16.4.39
  • affected9.16.4.42
  • affected9.16.4.48
  • affected9.16.4.55
  • affected9.16.4.57
  • affected9.16.4.61
  • affected9.16.4.62
  • affected9.16.4.67
  • affected9.16.4.70
  • affected9.16.4.71
  • affected9.16.4.76
  • affected9.16.4.82
  • affected9.16.4.84
  • affected9.17.1.20
  • affected9.17.1.30
  • affected9.17.1.33
  • affected9.17.1.39
  • affected9.17.1.45
  • affected9.17.1.46
  • affected9.18.1.3
  • affected9.18.2
  • affected9.18.2.5
  • affected9.18.2.7
  • affected9.18.2.8
  • affected9.18.3
  • affected9.18.3.39
  • affected9.18.3.46
  • affected9.18.3.53
  • affected9.18.3.55
  • affected9.18.3.56
  • affected9.18.4
  • affected9.18.4.5
  • affected9.18.4.8
  • affected9.18.4.22
  • affected9.18.4.24
  • affected9.18.4.29
  • affected9.18.4.34
  • affected9.18.4.40
  • affected9.18.4.47
  • affected9.18.4.50
  • affected9.18.4.52
  • affected9.18.4.53
  • affected9.18.4.57
  • affected9.19.1
  • affected9.19.1.5
  • affected9.19.1.9
  • affected9.19.1.12
  • affected9.19.1.18
  • affected9.19.1.22
  • affected9.19.1.24
  • affected9.19.1.27
  • affected9.19.1.28
  • affected9.19.1.31
  • affected9.19.1.37
  • affected9.19.1.38
  • affected9.19.1.42
  • affected9.20.1
  • affected9.20.1.5
  • affected9.20.2
  • affected9.20.2.10
  • affected9.20.2.21
  • affected9.20.2.22
  • affected9.20.3
  • affected9.20.3.4
  • affected9.20.3.7
  • affected9.20.3.9
  • affected9.20.3.10
  • affected9.20.3.13
  • affected9.20.3.16
  • affected9.20.3.20
  • affected9.22.1.1
  • affected9.22.1.3
  • affected9.22.1.2
  • affected9.22.1.6
  • affected9.22.2
  • affected9.22.2.4
  • affected9.23.1
  • affected9.23.1.3
Cisco Cisco Secure Firewall Threat Defense (FTD) Software
  • affected6.4.0.16
  • affected6.4.0.17
  • affected6.4.0.18
  • affected7.0.4
  • affected7.0.5
  • affected7.0.6
  • affected7.0.6.1
  • affected7.0.6.2
  • affected7.0.6.3
  • affected7.0.7
  • affected7.0.8
  • affected7.0.8.1
  • affected7.1.0.3
  • affected7.2.1
  • affected7.2.2
  • affected7.2.3
  • affected7.2.4
  • affected7.2.4.1
  • affected7.2.5
  • affected7.2.5.1
  • affected7.2.6
  • affected7.2.7
  • affected7.2.5.2
  • affected7.2.8
  • affected7.2.8.1
  • affected7.2.9
  • affected7.2.10
  • affected7.2.10.2
  • affected7.3.0
  • affected7.3.1
  • affected7.3.1.1
  • affected7.3.1.2
  • affected7.4.0
  • affected7.4.1
  • affected7.4.1.1
  • affected7.4.2
  • affected7.4.2.1
  • affected7.4.2.2
  • affected7.4.2.3
  • affected7.4.2.4
  • affected7.6.0
  • affected7.6.1
  • affected7.6.2
  • affected7.6.2.1
  • affected7.7.0
  • affected7.7.10
  • affected7.7.10.1

As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.

how to fix
Remediation steps are tailored for users whose stack is affected. Add this technology to your stack to see the fix checklist.
references
NVDCVE.orgCVE DetailsSource
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