Threats / Cisco / CVE-2025-20333
CVE-2025-20333
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
Cisco Secure Firewall Adaptive Security Appliance and Threat vulnerability
Buffer overflow in Cisco Secure Firewall ASA and FTD VPN web server enables remote code execution. Actively exploited in the wild.
Verdict
Today item — known-exploited.
A buffer overflow in the VPN web server component allows unauthenticated remote attackers to execute arbitrary code on affected Cisco firewalls. Active exploitation demonstrates immediate risk to perimeter security infrastructure.
CISA KEV Yes · 2025-09-255EPSS 0.70651 (verify live)6Exploit Public PoC7CVSS 9.93CISA SSVC Exploitation: active · Automatable: no · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Public proof-of-concept exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
26 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 2025-09-25).
Probability (EPSS)
EPSS 0.70651 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 9.9 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H) · Affected: Cisco, Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-120 Buffer Copy without Size Check — weakness family: Memory safety.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: totalCISA'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.
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 request to the VPN web server that overflows a buffer and injects shellcode.
Business
Perimeter security is compromised, enabling lateral movement into the protected network.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I gain code execution on the firewall appliance with the privileges of the web server process.
Business
Attackers obtain a foothold to pivot deeper into infrastructure or exfiltrate traffic passing through the firewall.
3
Lateral reach — past segmentation narrative 3
Attacker
I chain this vulnerability with CVE-2025-20362 to escalate privileges or bypass additional security controls.
Business
Complete compromise of the firewall enables full network visibility and control over encrypted VPN traffic.
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
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