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Full vulnerability report · 2021
CVE-2021-1612High confidence

Cisco IOS XE SD-WAN Software Arbitrary File Overwrite Vulnerability

Cisco · Cisco IOS XE SD-WAN Software

Official source article: Cisco CISCO-SA-SD-WAN-GJR5PGOM ↗. Check the applicable product and release in the original source.

5.5MediumCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 45 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Low, lowered one band.downgradedsince 7 Nov 2024

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • Exploitation requires an existing local or physical foothold with privileges.
  • EPSS is 0.25% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Cisco Cisco IOS XE SD-WAN Software and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: No default targetRemediation target: Normal maintenance

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 45 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
cisco-sa-sd-wan-GjR5pGOm · CSAF 2.0 · revision 1.0.0 · finalCisco PSIRTCisco IOS XE SD-WAN Arbitrary File Overwrite Vulnerability
45 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco Catalyst IR1100 Rugged Series Routers
  • Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco Cloud Services Router 1000V Series
  • Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco 1000 Series Integrated Services Routers
  • Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco ASR 1000 Series Aggregation Services Routers
  • Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco 4000 Series Integrated Services Routers
  • Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco Integrated Services Virtual Router
  • Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco Catalyst IR1100 Rugged Series Routers
  • Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco Cloud Services Router 1000V Series
  • Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco 1000 Series Integrated Services Routers
  • Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco ASR 1000 Series Aggregation Services Routers
  • Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco 4000 Series Integrated Services Routers
  • Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco Integrated Services Virtual Router
Summary
Complete.
Remediation
Cisco has released software updates that address this vulnerability.
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2021-7079

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 45 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

A vulnerability in the Cisco IOS XE SD-WAN Software CLI could allow an authenticated, local attacker to overwrite arbitrary files on the local system. This vulnerability is due to improper access controls on files within the local file system. An attacker could exploit this vulnerability by placing a symbolic link in a specific location on the local file system. A successful exploit could allow the attacker to overwrite arbitrary files on an affected device.

What

A vulnerability in the Cisco IOS XE SD-WAN Software CLI could allow an authenticated, local attacker to overwrite arbitrary files on the local system. This vulnerability is due to improper access controls on files within the local file system. An attacker could exploit this vulnerability by placing a symbolic link in a specific location on the local file system. A successful exploit could allow the attacker to overwrite arbitrary files on an affected device.

Why

The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

A vulnerability in the Cisco IOS XE SD-WAN Software CLI could allow an authenticated, local attacker to overwrite arbitrary files on the local system. This vulnerability is due to improper access controls on files within the local file system. An attacker could exploit this vulnerability by placing a symbolic link in a specific location on the local file system. A successful exploit could allow the attacker to overwrite arbitrary files on an affected device.

Why

The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
local access → UNIX Symbolic Link (Symlink) Following → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Local
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-61 ↗

CWE-61: UNIX Symbolic Link (Symlink) Following. The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.IHighIntegrity impact: A successful attack can cause a major loss.ANoneAvailability impact: No direct loss is represented by this metric.
Post-exploitation / living off the land
The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
CWE-61
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

Cyber Security Agency of Singapore · English · CSA-SB-20210929Security Bulletin 29 Sep 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 29 Sep 2021, published on 29 September 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-012518Cisco IOS XE SD-WAN ソフトウェア CLI におけるリンク解釈に関する脆弱性

Cisco IOS XE SD-WAN ソフトウェア CLI には、リンク解釈に関する脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix availability varies by product
Affected
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 23 Sept 2021 · Last source change 7 Nov 2024, 21:51 UTC · CWE-61 · UNIX Symbolic Link (Symlink) Following

CVE recordCVE.org · 5.1
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2021-7079
Product sourceVendor CSAF · Cisco PSIRT
Remediation sourceVendor CSAF · Cisco PSIRT
CWE sourceCNA
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    Cisco IOS XE Catalyst SD-WAN 16.9.1 when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.1 when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.1 when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.1 when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.9.2 when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.2 when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.2 when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.2 when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.9.3 when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.3 when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.3 when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.3 when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.9.4 when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.4 when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.4 when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.9.4 when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.10.1 when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.10.1 when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.10.1 when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.10.1 when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.10.2 when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.10.2 when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.10.2 when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.10.2 when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.10.3 when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.10.3 when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.10.3 when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.10.3 when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.10.3a when installed on Cisco Cloud Services Router 1000V Series; Cisco IOS XE Catalyst SD-WAN 16.10.3a when installed on Cisco 1000 Series Integrated Services Routers; and 74 more
    After
    Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco Catalyst IR1100 Rugged Series Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco Cloud Services Router 1000V Series; Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco Catalyst IR1100 Rugged Series Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco Cloud Services Router 1000V Series; Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco Catalyst IR1100 Rugged Series Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco Cloud Services Router 1000V Series; Cisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco Catalyst IR1100 Rugged Series Routers; Cisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco Cloud Services Router 1000V Series; Cisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco Integrated Services Virtual Router; Cisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco Catalyst IR1100 Rugged Series Routers; Cisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco Cloud Services Router 1000V Series; Cisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco 1000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco ASR 1000 Series Aggregation Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco 4000 Series Integrated Services Routers; Cisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco Integrated Services Virtual Router; and 15 more
    Cisco PSIRT ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2021-7079↗Vendor CSAF · Cisco PSIRT · Cisco CISCO-SA-SD-WAN-GJR5PGOM↗CVE authority or vendor reference · Cisco CISCO-SA-SD-WAN-GJR5PGOM↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2021-1612 · cve.blacktree.nl