Threats / Cisco / CVE-2024-20353
CVE-2024-20353
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
Cisco Adaptive Security Appliance (ASA) and Firepower Threat vulnerability
Cisco ASA and FTD contain an infinite loop vulnerability (CWE-835) enabling remote denial of service. The flaw is exploited in the wild.
Verdict
Today item — known-exploited.
A remote attacker can trigger an infinite loop condition in Cisco ASA and FTD devices, causing them to become unresponsive and disrupting network security operations and traffic inspection.
CISA KEV Yes · 2024-04-245EPSS 0.70686 (verify live)6CVSS 8.63CISA SSVC Exploitation: active · Automatable: yes · Impact: partial4
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
17 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2024-04-24).
Probability (EPSS)
EPSS 0.70686 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 8.6 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H) · Affected: Cisco, Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD). Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-835 CWE-835.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog the same day the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
WeaknessCWE-835 · CWE-835
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious network packet or request designed to trigger the infinite loop condition in the target device.
Business
Network security infrastructure becomes unavailable, halting threat detection and firewall policy enforcement.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I send the crafted input to the vulnerable ASA or FTD instance, causing it to enter an infinite loop state.
Business
The affected security appliance stops processing legitimate traffic, creating a denial of service condition.
3
Lateral reach — past segmentation narrative 3
Attacker
I observe the device becoming unresponsive and confirm the denial of service impact.
Business
Organizations lose visibility and control over network traffic until the device is manually recovered or rebooted.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by ciscoCNA
Credited with finding itNo finder is named in the public CVE record or the scanned vendor advisory — attribution scoped to the sources checked.
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
npub1j7gt9ky7sfcrjn8jjee6693dkzvk4rahs0fk2suu7968dfns62zs3mqm3y.