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CVE Record

CVE-2020-3373: Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software IP Fragment Memory Leak Vulnerability

A vulnerability in the IP fragment-handling implementation of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a memory leak on an affected device. This memory leak could prevent traffic from being processed through the device, resulting in a denial of service (DoS) condition. The vulnerability is due to improper error handling when specific failures occur during IP fragment reassembly. An attacker could exploit this vulnerability by sending crafted, fragmented IP traffic to a targeted device. A successful exploit could allow the attacker to continuously consume memory on the affected device and eventually impact traffic, resulting in a DoS condition. The device could require a manual reboot to recover from the DoS condition. Note: This vulnerability applies to both IP Version 4 (IPv4) and IP Version 6 (IPv6) traffic.

HighCVSS 8.6Not KEV-listedUpdated
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This flaw can let an unauthenticated remote attacker exhaust memory on Cisco ASA or FTD devices by sending crafted fragmented IP traffic. The business impact is service disruption: the device may stop processing traffic and could require a manual reboot.

Executive priority

Treat as high priority for perimeter firewalls and VPN/security gateways because successful exploitation can interrupt traffic flow. Prioritize externally exposed ASA and FTD assets first, then internal high-availability chokepoints.

Technical view

CVE-2020-3373 is an IP fragment reassembly memory leak in Cisco ASA Software and FTD Software. Improper error handling during specific fragment reassembly failures can continuously consume memory. It affects IPv4 and IPv6 traffic and is rated CVSS 8.6 for high availability impact.

Likely exposure

Exposure is most relevant for Cisco ASA or FTD devices that process untrusted IPv4 or IPv6 traffic. The source bundle does not provide exact affected release ranges, so teams must confirm exposure against Cisco's advisory.

Exploitation context

The bundle describes remote, unauthenticated exploitation using crafted fragmented IP traffic. It does not cite CISA KEV listing or other evidence of active exploitation, so active exploitation should not be assumed from these sources.

Researcher notes

The source maps this to CWE-400 resource consumption. The key technical condition is improper error handling during IP fragment reassembly failure. Exact affected versions and fixed releases are not present in the bundle; rely on Cisco's advisory for those details.

Mitigation direction

  • Identify Cisco ASA and FTD devices in internet-facing and perimeter roles.
  • Check Cisco's advisory for affected releases and vendor-recommended fixes.
  • Upgrade or apply Cisco-recommended mitigation after confirming device applicability.
  • Monitor memory usage and traffic processing health until remediation is complete.
  • Prepare operational reboot procedures for affected devices if DoS symptoms appear.

Validation and detection

  • Compare deployed ASA and FTD versions against Cisco advisory applicability.
  • Confirm whether devices process untrusted IPv4 or IPv6 fragmented traffic.
  • Review monitoring for abnormal memory growth or traffic processing failures.
  • Verify remediation status after upgrade or vendor-guided mitigation.
  • Document remaining devices where version exposure is still unknown.
Prepared
Confidence
medium
Sources
3

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-400: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2020-3373 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
8.6 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.6CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H3.94Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

8.6High
CVSS 3.1 vector shape for CVE-2020-3373Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone
Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
CiscoCisco Adaptive Security Appliance (ASA) Softwaren/aListed
Weakness

CWE details

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-400 · source CWE mapping

Uncontrolled Resource Consumption

Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.