dbcve.org
Ios XeOperating system · Cisco

CVE-2021-1529

HIGH · 7.8 CVSS v3.1 Published 2021-10-21
Fix available
A fix is available. Upgrade to 17.2.3 / 17.3.4 or later.
See remediation →
80/100
Remediation priority · High
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 CLI of Cisco IOS XE SD-WAN Software could allow an authenticated, local attacker to execute arbitrary commands with root privileges. The vulnerability is due to insufficient input validation by the system CLI. An attacker could exploit this vulnerability by authenticating to an affected device and submitting crafted input to the system CLI. A successful exploit could allow the attacker to execute commands on the underlying operating system with root privileges.

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

A command injection vulnerability exists in the CLI of Cisco IOS XE SD-WAN Software due to insufficient input validation. An authenticated local attacker with valid device credentials can submit crafted input to the system CLI, bypassing normal command restrictions to execute arbitrary operating system commands with root-level privileges.

MitigationApply the Cisco IOS XE software update (refer to Cisco advisory) and restrict CLI access to only trusted, authorized personnel using least-privilege principles.

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 XeOperating system
Affected:>= 16.12, <= 17.0>= 17.2, < 17.2.3>= 17.3, < 17.3.4>= 17.4, < 17.4.2>= 17.5, < 17.5.1a= 17.6.0
Ios Xe Sd WanOperating system
Affected:>= 17.2.1r

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/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 checks

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

  1. Identify the installed Cisco IOS XE version
    Execute 'show version' or 'show version | include Version' in the CLI to retrieve the running software version
    Affected if The displayed version falls within any of these ranges: 16.12 to 17.0, 17.2 to 17.2.2, 17.3 to 17.3.3, 17.4 to 17.4.1, 17.5 to 17.5.1, or equals 17.6.0
  2. Determine if SD-WAN feature is enabled
    Execute 'show sdwan version' or 'show sdwan running-config' in the CLI. If these commands are not available or return error, SD-WAN may not be configured
    Affected if SD-WAN is actively configured or running on the device, as the vulnerability exists specifically in the SD-WAN CLI component
  3. Verify SD-WAN software version if separate
    If running SD-WAN as a separate image or package, execute 'show version' specific to the sd-wan image and note the version number
    Affected if The SD-WAN software version is 17.2.1r or higher (any version up to and including the latest in the 17.x train)
  4. Confirm CLI access exists for local authenticated users
    Review user accounts and privilege levels using 'show users' and 'show privilege' to determine if multiple local accounts exist with CLI access
    Affected if The device has local user accounts with privilege level 15 (or lower with CLI access) that could potentially exploit this vulnerability, since it requires authenticated local access

You are affected if your device runs Cisco IOS XE version within the specified vulnerable ranges AND has SD-WAN functionality enabled, allowing an authenticated local user to access the CLI.

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 17.2.3 / 17.3.4 / 17.4.2 or later
Fixed in 17.2.317.3.417.4.2
Interim mitigation

Apply the Cisco IOS XE software update (refer to Cisco advisory) and restrict CLI access to only trusted, authorized personnel using least-privilege principles.

Recommended fix High confidence

17.2.3 (for 17.2.x), 17.3.4 (for 17.3.x), or 17.4.2 (for 17.4.x); or migrate to 17.5+ if available

  1. 1. Identify the current IOS XE version using 'show version' command
  2. 2. Determine the appropriate upgrade path based on current version (17.2.x -> 17.2.3, 17.3.x -> 17.3.4, or 17.4.x -> 17.4.2)
  3. 3. Download the corresponding fixed Cisco IOS XE software from Cisco.com or your authorized supplier
  4. 4. Verify the software image integrity using MD5/SHA256 checksums provided by Cisco
  5. 5. Backup the current configuration using 'copy running-config startup-config' or 'archive config'
  6. 6. Upload the new IOS XE image to the device using 'copy <url> flash:'
  7. 7. Configure the boot system to use the new image: 'boot system flash:<image_name>'
  8. 8. Reload the device using 'reload' command
Caveat Cisco IOS XE upgrades typically preserve configuration but always review release notes for migration-specific caveats between major version trains

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

Fix this in Ios Xe Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,980
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,168.

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-2021-1529 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