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.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-552: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupFile 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.
Open ATT&CK lookupCVE-2021-1256 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- 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
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.
CVSS vector scores
1 official scoreWe 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.
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H0.85.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6MediumVector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20210428 Cisco Firepower Threat Defense Software Command File Overwrite VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
- https://kc.mcafee.com/corporate/index?page=content&id=SB10382CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
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.
