CVE-2025-20217
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA vulnerability in the packet inspection functionality of the Snort 3 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to incorrect processing of traffic that is inspected by an affected device. An attacker could exploit this vulnerability by sending crafted traffic through the affected device. A successful exploit could allow the attacker to cause the affected device to enter an infinite loop while inspecting traffic, resulting in a DoS condition. The system watchdog will restart the Snort process automatically.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThis is a denial of service vulnerability in the Snort 3 Detection Engine packet inspection functionality of Cisco Secure Firewall Threat Defense (FTD). An unauthenticated remote attacker can send specially crafted traffic through the affected device, causing an infinite loop in the Snort inspection process. The system watchdog automatically restarts the Snort process as a recovery mechanism, but the device remains unavailable during the restart.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Identify the device as Cisco FTDConfirm the device is Cisco Secure Firewall Threat Defense (FTD) and not another product like ASA or Firepower Management Center. Use 'show version' or check the device model.Affected if The device is not Cisco Secure Firewall Threat Defense (FTD)
-
Check the FTD software versionRun 'show version' on the FTD CLI or check the version through Firepower Management Center. Compare the installed version against the affected version ranges provided by Cisco's security advisory.Affected if The installed FTD version falls within the vulnerable version range and has not been patched
-
Verify Snort 3 inspection is enabledCheck the access control policy or intrusion policy configuration on the FTD device. Use 'show running-config | include snort' or review the inspection rules in the policy.Affected if Snort 3 inspection is enabled and processing traffic (this is required for the vulnerability to be exploitable)
-
Review system logs for Snort process issuesCheck system logs, crashinfo, or the Snort process health status using 'show snort statistics' or reviewing /var/log/messages for watchdog restarts.Affected if There are recurring Snort process crashes or watchdog-triggered restarts indicating potential exploitation
A user is affected if the device is running a vulnerable Cisco FTD version with Snort 3 inspection enabled and processing traffic, as the crafted traffic would trigger the infinite loop condition.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply the vendor-supplied patch or upgrade to the fixed software version of Cisco FTD that addresses this vulnerability. Coordinate a maintenance window for the update given the potential for service interruption.
- Consultation3.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,832.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-20217 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-20217 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data