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CVE Record

CVE-2021-1256: Cisco Firepower Threat Defense Software Command File Overwrite Vulnerability

A 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.

MediumCVSS 6Not KEV-listedUpdated
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-1256 lets a logged-in local user on Cisco Firepower Threat Defense overwrite files through a vulnerable CLI command. The attacker needs valid device credentials, reducing broad internet risk, but successful abuse can damage system integrity or stability.

Executive priority

Prioritize as a controlled-access infrastructure risk. It is not described as remotely exploitable without credentials, but affected security appliances are sensitive assets, and file overwrite can undermine availability or operational trust.

Technical view

The issue is insufficient file path validation in a specific Cisco FTD CLI command. Crafted input using directory traversal can overwrite arbitrary files on the affected device. CVSS 3.1 is 6.0: local attack vector, low complexity, high privileges required, no user interaction, high integrity and availability impact, no confidentiality impact.

Likely exposure

Exposure is limited to Cisco Firepower Threat Defense Software devices where an attacker already has valid local CLI credentials. The provided bundle does not identify exact affected or fixed versions, so vulnerability managers must verify against Cisco’s advisory and local device inventory.

Exploitation context

The bundle does not report active exploitation, and the CVE is not marked KEV. Abuse requires authenticated local access and crafted CLI input, so insider misuse, stolen admin credentials, or overprivileged operational accounts are the main concern.

Researcher notes

Evidence supports arbitrary file overwrite via directory traversal in a Cisco FTD CLI command. Exact vulnerable versions, fixed versions, workarounds, and exploit prevalence are not present in the supplied bundle. Do not assume broader Cisco product impact from this record alone.

Mitigation direction

  • Check Cisco’s advisory for affected releases, fixed releases, and any workarounds.
  • Restrict FTD CLI access to trusted administrators only.
  • Remove stale, shared, or unnecessary device credentials.
  • Review administrative access controls and logging coverage.
  • Investigate unexplained file changes or device instability promptly.

Validation and detection

  • Inventory Cisco Firepower Threat Defense deployments and software versions.
  • Compare deployed versions against Cisco’s advisory guidance.
  • Review who has CLI access to each affected device.
  • Check logs for unexpected administrative CLI activity.
  • Confirm monitoring covers device instability and configuration integrity signals.
Prepared
Confidence
high
Sources
4

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-552: Exact CWE lookup

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description · low confidence lookup

File access behavior lookup

The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2021-1256 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
6 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
6CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H0.85.2Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

6Medium
CVSS 3.1 vector shape for CVE-2021-1256Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
CiscoCisco Firepower Threat Defense Softwaren/aListed
Weakness

CWE details

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-552 · source CWE mapping

Files or Directories Accessible to External Parties

Files or Directories Accessible to External Parties represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.