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Ios Xe Sd WanOperating system · Cisco

CVE-2021-34724

MEDIUM · 6.0 CVSS v3.1 Published 2021-09-23
Fix available
A fix is available. Upgrade to after 17.3.1a or later.
See remediation →
62/100
Remediation priority · Elevated
Zero-click

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 · unedited
A vulnerability in the Cisco IOS XE SD-WAN Software CLI could allow an authenticated, local attacker to elevate privileges and execute arbitrary code on the underlying operating system as the root user. An attacker must be authenticated on an affected device as a PRIV15 user. This vulnerability is due to insufficient file system protection and the presence of a sensitive file in the bootflash directory on an affected device. An attacker could exploit this vulnerability by overwriting an installer file stored in the bootflash directory with arbitrary commands that can be executed with root-level privileges. A successful exploit could allow the attacker to read and write changes to the configuration database on the 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 confidence

Local privilege escalation vulnerability in Cisco IOS XE SD-WAN Software CLI where an authenticated PRIV15 user can overwrite installer files in the bootflash directory with malicious commands that execute with root-level privileges, allowing read/write access to the configuration database.

MitigationApply Cisco IOS XE software updates addressing CVE-2021-34724; restrict PRIV15-level access to trusted personnel and monitor for unauthorized bootflash file modifications.

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
Ios Xe Sd WanOperating system
Affected:<= 17.3.1a

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
Local
Complexity
Low
Privileges
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the software type
    Run 'show version' or 'show system' to confirm the device is running Cisco IOS XE SD-WAN Software
    Affected if The output shows IOS XE SD-WAN rather than standard IOS XE
  2. Check the installed version
    Run 'show version' and locate the version string (for example, 17.3.1, 17.3.1a, or later)
    Affected if The version number is 17.3.1a or earlier (any version <= 17.3.1a)
  3. Confirm PRIV15 user access exists
    Run 'show privilege' or 'show running-config | include username' to identify if any users with PRIV15 privilege level are configured
    Affected if Any user account with privilege level 15 is present on the device
  4. Inspect bootflash for installer files
    Run 'dir bootflash:' to list files in bootflash and check for unexpected installer files (.bin, .pkg, .tar) that were not intentionally deployed
    Affected if There are installer files in bootflash that were not explicitly installed by the administrator

A user is affected if the device runs Cisco IOS XE SD-WAN version 17.3.1a or earlier and has PRIV15 user accounts configured, making unauthorized bootflash file modifications possible.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Upgrade available Upgrade to a release after 17.3.1a
Interim mitigation

Apply Cisco IOS XE software updates addressing CVE-2021-34724; restrict PRIV15-level access to trusted personnel and monitor for unauthorized bootflash file modifications.

Recommended fix Moderate confidence

Cisco IOS XE SD-WAN 17.3.2 or later (verify exact version in Cisco Security Advisory)

  1. 1. Identify the current Cisco IOS XE SD-WAN version running on the affected device using 'show version' command
  2. 2. Access the Cisco Security Advisories page at tools.cisco.com and search for CVE-2021-34724 to confirm the exact fixed release
  3. 3. Plan an upgrade window during maintenance period as this requires device reload
  4. 4. Download the fixed IOS XE SD-WAN release (typically 17.3.2 or later) from Cisco Software Download center
  5. 5. Verify the image integrity using the MD5/SHA256 checksum provided by Cisco
  6. 6. Copy the new image to bootflash using 'copy <source> bootflash:'
  7. 7. Set the boot variable to point to the new image using 'boot system bootflash:<new-image-name>'
  8. 8. Save configuration with 'write memory'
Caveat Standard IOS XE upgrade considerations apply - verify compatibility with other SD-WAN components and ensure configuration compatibility before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Ios Xe Sd Wan Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-34724 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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