CASCACascade Atlas

Evidence dossier

CVE-2024-20481

A vulnerability in the Remote Access VPN (RAVPN) service of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an…

Exploited in the wild (CISA KEV since Oct 24, 2024). NVD reports CVSS 3.1 5.8. EPSS estimates 15.9% exploit likelihood as of Aug 27, 2026.

66.0–77.5Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

A vulnerability in the Remote Access VPN (RAVPN) service of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) of the RAVPN service. This vulnerability is due to resource exhaustion. An attacker could exploit this vulnerability by sending a large number of VPN authentication requests to an affected device. A successful exploit could allow the attacker to exhaust resources, resulting in a DoS of the RAVPN service on the affected device. Depending on the impact of the attack, a reload of the device may be required to restore the RAVPN service. Services that are not related to VPN are not affected. Cisco Talos discussed these attacks in the blog post Large-scale brute-force activity targeting VPNs, SSH services with commonly used login credentials.

State
PUBLISHED
Published
Oct 23, 2024
Updated
Oct 21, 2025
Evidence coverage
92%

Evidence chronology

What was known when

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  1. Source dateSource date omittedFirst observed by CASCA
    CISA-ADP

    Record text: CISA ADP Vulnrichment

    Inspect raw assertion
    Field
    container
    Value
    CISA ADP Vulnrichment
    Original evidence ↗
  2. Source dateSource date omittedFirst observed by CASCA
    cisco

    Record text: A vulnerability in the Remote Access VPN (RAVPN) service of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) of the RAVPN service. This vulnerability is due to resource exhaustion. An attacker could exploit this vulnerability by sending a large number of VPN authentication requests to an affected device. A successful exploit could allow the attacker to exhaust resources, resulting in a DoS of the RAVPN service on the affected device. Depending on the impact of the attack, a reload of the device may be required to restore the RAVPN service. Services that are not related to VPN are not affected. Cisco Talos discussed these attacks in the blog post Large-scale brute-force activity targeting VPNs, SSH services with commonly used login credentials.

    Inspect raw assertion
    Field
    container
    Value
    A vulnerability in the Remote Access VPN (RAVPN) service of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) of the RAVPN service. This vulnerability is due to resource exhaustion. An attacker could exploit this vulnerability by sending a large number of VPN authentication requests to an affected device. A successful exploit could allow the attacker to exhaust resources, resulting in a DoS of the RAVPN service on the affected device. Depending on the impact of the attack, a reload of the device may be required to restore the RAVPN service. Services that are not related to VPN are not affected. Cisco Talos discussed these attacks in the blog post Large-scale brute-force activity targeting VPNs, SSH services with commonly used login credentials.
    Original evidence ↗
  3. Source dateFirst observed by CASCA
    CISA KEV

    Exploitation cataloged: Cisco ASA and FTD Denial-of-Service Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    Cisco ASA and FTD Denial-of-Service Vulnerability
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 15.85% probability · 96.63th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.158520000000; percentile 0.966310000000
    Original evidence ↗
ExploitationCatalog member

CISA KEV · catalog date Oct 24, 2024 · first observed Jul 19, 2026

Exploit likelihood15.85%

FIRST EPSS · score date Aug 27, 2026 · 96.6th percentile · first observed Aug 27, 2026

SeverityCVSS 5.8

NVD · CVSS 3.1 · first observed Jul 19, 2026 · same-version scores align in this snapshot

Evidence detail

Source limits and decisions

Why each evidence state has this value

Outside this view’s verified evidence

Reason detail begins outside this selected snapshot; the state remains source-bound.

Source comparison

Who said what

CISA-ADPIndependent enrichment
Record text

CISA ADP Vulnrichment

Inspect raw assertion
Field
container
Value
CISA ADP Vulnrichment
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
ciscoOriginal assertion
Record text

A vulnerability in the Remote Access VPN (RAVPN) service of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) of the RAVPN service. This vulnerability is due to resource exhaustion. An attacker could exploit this vulnerability by sending a large number of VPN authentication requests to an affected device. A successful exploit could allow the attacker to exhaust resources, resulting in a DoS of the RAVPN service on the affected device. Depending on the impact of the attack, a reload of the device may be required to restore the RAVPN service. Services that are not related to VPN are not affected. Cisco Talos discussed these attacks in the blog post Large-scale brute-force activity targeting VPNs, SSH services with commonly used login credentials.

Inspect raw assertion
Field
container
Value
A vulnerability in the Remote Access VPN (RAVPN) service of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) of the RAVPN service. This vulnerability is due to resource exhaustion. An attacker could exploit this vulnerability by sending a large number of VPN authentication requests to an affected device. A successful exploit could allow the attacker to exhaust resources, resulting in a DoS of the RAVPN service on the affected device. Depending on the impact of the attack, a reload of the device may be required to restore the RAVPN service. Services that are not related to VPN are not affected. Cisco Talos discussed these attacks in the blog post Large-scale brute-force activity targeting VPNs, SSH services with commonly used login credentials.
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
CISA KEVOriginal assertion
Exploitation cataloged

Cisco ASA and FTD Denial-of-Service Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
Cisco ASA and FTD Denial-of-Service Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

15.85% probability · 96.63th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.158520000000; percentile 0.966310000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
289Underlying assertions
2Canonical products
289Target assertions
0Constraint assertions

Grouped from 2 configuration nodes in this exact snapshot. Visual grouping is navigational; asset exposure and root cause require cited evidence.

Identity source boundaries
  • Cpe dictionary1,775,266 records · observed through 2026-07-21T06:45:29.809Z27d65b0f-b718-4b4f-bb79-c47c68d09dfa
  • Cpe match643,502 records · observed through 2026-07-21T08:13:17.697Z955dae73-7302-438b-aee1-058d7cc5d48e

291 scope groups

CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.35
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.35"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.38
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.38"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.1
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.1"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.1.5
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.1.5"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.1.7
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.1.7"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.8
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.8"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.14
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.14"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.15
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.15"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.17
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.17"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.20
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.20"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.24
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.24"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.26
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.26"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.28
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.28"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.2.33
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.2.33"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.3.8
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.3.8"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.3.11
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.3.11"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.3.14
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.3.14"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.3.16
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.3.16"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.3.18
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.3.18"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.3.21
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.3.21"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.3
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.3"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.3.26
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.3.26"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.3.29
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.3.29"}]
CISA-ADP · source assertedciscoadaptive_security_appliance_softwareDirect source scope
Affected: 9.8.4
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "9.8.4"}]

Affected-product evidence

Accepted scope and product mapping

0 canonical links · 0 source-reported links

Applicability remains source-scoped; safety and exposure remain unassessed.

Assessments

CVSS by origin

5.8
NVDCVSS 3.1 · role Primary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
5.8
psirt@cisco.comCVSS 3.1 · role Secondary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
5.8
ciscoCVSS 3.1 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L

Evidence boundaries

  • KEV membership is authoritative for the catalog, not proof of exposure in any environment.
  • EPSS is a dated model probability and not an individual-environment prediction.
  • Affected or fixed status applies only to the exact cited product and version scope; remaining scope stays source-scoped.
  • NVD-carried upstream facts remain derivative; independent corroboration requires a separately authored source.
  • Only NVD metrics validated under the generation-bound calculator are Public Priority eligible; direct CVE record metrics remain display-only.
  • NVD CVSS source eligibility is closed: NVD-authored, exact record-source, or registered same-CVE container origin; unmapped sources remain display-only.
  • Affected-product evidence remains source-scoped; canonical linkage is required before applicability scoring.
  • Core replay supports the active and immediately prior generation; retrospective valid-at replay is deferred.
  • OSV aggregation and OSV-converted NVD material are not independent corroboration.
  • Red Hat facts are vendor assertions for the exact supplied products.
  • Nonmembership and not-yet-observed states are not proof of safety.