Medium File handling

CVE-2026-20161 — Cisco ThousandEyes Enterprise Agent Arbitrary File Overwrite Vulnerability

A vulnerability in the CLI of Cisco ThousandEyes Enterprise Agent could allow an authenticated, local attacker with low privileges to overwrite arbitrary files on the local system of an affected device. This vulnerability is due to improper access controls on files that are on the local file system of an affected device. 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 bypass file system permissions and overwrite arbitrary files on the affected device.

Published Apr 15, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: cisco

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.1% (30-day exploitation probability)+0
Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.13%

ahead of 2% of scored CVEs · Oct 14, 2026

Affects

Cisco

Cisco ThousandEyes Enterprise Agent

CVSS base

5.5

Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Cisco Cisco ThousandEyes Enterprise Agent).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (file handling), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Cisco	Cisco ThousandEyes Enterprise Agent	version Agent 5.0version Agent 4.4.4version Agent 4.4.3version Agent 4.4.2version Agent 4.2version Agent 4.1version Agent 4.0version Agent 5.1 and 1 more version Agent 5.1.2	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.5	CVSS 3.1	Medium	1.8	3.6	psirt@cisco.com via NIST National Vulnerability Database
5.5	CVSS 3.1	Medium	—	—	cisco via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N (score shown at the top: psirt@cisco.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-59 · Link Following

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.13%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
Monitor file creation in web directories and paths with traversal sequences (../).

endpoint telemetry (EDR)file integrity (FIM)

Timeline

What happened to this CVE, newest first.

2026
Affected products added · cisco/cisco thousandeyes enterprise agent
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 5.5
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Awaiting Analysis
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Apr 15, 2026 · cisco

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-te-agentfilewr
NIST National Vulnerability Database

Elsewhere on this site

Cisco
every CVE for this vendor

File handling
same class

CWE-59
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-20199 Injection in Cisco Thousandeyes Virtual Appliance May 20, 2026
Medium CVE-2026-20206 Cisco ThousandEyes BrowserBot Command Injection Vulnerability May 20, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-20161 is "Cisco ThousandEyes Enterprise Agent Arbitrary File Overwrite Vulnerability", rated Medium. It affects Cisco ThousandEyes Enterprise Agent (Cisco); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.5 describes technical severity. EPSS 0.13% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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