Secure Firewall Threat DefenseApplication · Cisco
CVE-2020-3253
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 support tunnel feature of Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, local attacker to access the shell of an affected device even though expert mode is disabled. The vulnerability is due to improper configuration of the support tunnel feature. An attacker could exploit this vulnerability by enabling the support tunnel, setting a key, and deriving the tunnel password. A successful exploit could allow the attacker to run any system command with root access on an affected device.
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 confidenceA vulnerability in Cisco FTD's support tunnel feature allows authenticated local attackers to bypass expert mode restrictions. By enabling the support tunnel, setting a key, and deriving the tunnel password, attackers can execute arbitrary system commands with root privileges on affected devices.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Secure Firewall Threat DefenseApplication
< 6.5.0CVSS 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
- Local
- Complexity
- Low
- Privileges
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/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.
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Identify FTD versionUse the CLI command 'show version' on the FTD device or check the version via Firepower Management Center. Locate the displayed software version number.Affected if The installed version is below 6.5.0 (any version starting with 6.4.x or earlier)
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Confirm support tunnel is configuredExamine the FTD configuration for support tunnel settings. This may appear in the system configuration or through CLI commands that display tunnel-related settings.Affected if The support tunnel feature is enabled or has been previously configured on the device
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Verify expert mode statusCheck whether expert mode is available or enabled on the FTD device. This relates to the restricted shell that the vulnerability allows attackers to bypass.Affected if Expert mode is currently enabled or was recently disabled (the bypass still poses a risk if it was recently turned off)
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Review support tunnel password derivationInspect any configuration files or logs related to support tunnel password creation. The vulnerability involves deriving the tunnel password from an attacker-controlled key.Affected if Support tunnel passwords were set using a key that could have been manipulated or observed by a local attacker
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Check for unexpected local accountsSince the vulnerability allows root privilege escalation, review the system for any unauthorized or unexpected local user accounts that may indicate exploitation.Affected if Unexpected local accounts exist on the system with elevated privileges
You are affected if your FTD version is below 6.5.0 AND the support tunnel feature is or was enabled, regardless of expert mode's current state.
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 data6.5.0
Apply Cisco security updates for FTD that properly enforce expert mode restrictions on the support tunnel feature, or disable the support tunnel feature if not required and ensure expert mode remains disabled.
Fix this in Secure Firewall Threat Defense
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing4.0 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 $3,648.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-3253 — 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-2020-3253 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
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- Version or environment caveats, and links to real fixes
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