Secure Firewall Threat DefenseApplication · Cisco
CVE-2021-1256
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 CLI of Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, local attacker to overwrite files on the file system of an affected device by using directory traversal techniques. A successful exploit could cause system instability if important system files are overwritten. This vulnerability is due to insufficient validation of user input for the file path in a specific CLI command. An attacker could exploit this vulnerability by logging in to a targeted device and issuing a specific CLI command with crafted user input. A successful exploit could allow the attacker to overwrite arbitrary files on the file system of the affected device. The attacker would need valid user credentials on the 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 directory traversal vulnerability exists in the Cisco FTD CLI due to insufficient validation of user-supplied file paths in a specific CLI command. An authenticated local attacker can use traversal sequences (e.g., ../../../') to escape the intended directory and overwrite arbitrary files on the device filesystem, potentially overwriting critical system files and causing instability.
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
<= 6.4.0>= 6.6.0, < 6.6.4CVSS 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
- None
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/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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Check Firepower Threat Defense versionAccess the FTD CLI and run the command to display the system version (for example: 'show version' or 'system version'). Compare the displayed version number to the affected ranges.Affected if The installed version is 6.4.0 or earlier, OR the version is 6.6.0 through 6.6.3 (any version >= 6.6.0 but < 6.6.4).
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Identify the vulnerable CLI commandReview CLI command documentation or audit existing CLI scripts for file path parameters. Look for commands that accept file paths as arguments where traversal sequences could be supplied.Affected if A custom or third-party CLI command processes user-supplied file paths without sanitization.
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Verify access controls on CLI accessReview user accounts with CLI access and confirm which users can execute privileged commands. Check for any unauthorized or unexpected accounts.Affected if Multiple users or untrusted accounts have authenticated CLI access to the device.
You are affected if your Cisco FTD version is 6.4.0 or earlier, or between 6.6.0 and 6.6.3, and an authenticated user can access the vulnerable CLI command that accepts file path arguments.
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 data6.6.4
Apply the Cisco patch for CVE-2021-1256 and restrict CLI access to only trusted, authorized personnel to reduce the attack surface.
Fix this in Secure Firewall Threat Defense
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1256 — 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-2021-1256 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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- 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
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