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E1200 Firmware CVE-2018-3953

HIGH
OS Command Injection (CWE-78)
2018-10-17 talos-cna@cisco.com
7.2
CVSS 3.1 · NVD
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization OS command sanitization, avoid shell exec
MITRE ATT&CK

2 techniques across 1 tactic: Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Impact

CVSS score of 7.2 (HIGH). Attack characteristics: network attack vector, low complexity, high privileges required, no user interaction not required. Public proof-of-concept exploit code is available.

Exploit ScenarioDerived

A remote attacker could execute arbitrary operating system commands on the host by sending crafted requests to the affected application.

Act Now Prioritize within 24-48h. Why: HIGH severity + EPSS > 10%.
No patch listed yet 13.3% exploitation probability (EPSS)

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AnalysisAI

Devices in the Linksys ESeries line of routers (Linksys E1200 Firmware Version 2.0.09 and Linksys E2500 Firmware Version 3.0.04) are susceptible to OS command injection vulnerabilities due to. Rated high severity (CVSS 7.2), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and no vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Avoid passing user input to shell commands. Use language-specific APIs instead of shell execution. Apply strict input validation with allowlists.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as OS Command Injection (CWE-78), which allows attackers to execute arbitrary operating system commands on the host. Devices in the Linksys ESeries line of routers (Linksys E1200 Firmware Version 2.0.09 and Linksys E2500 Firmware Version 3.0.04) are susceptible to OS command injection vulnerabilities due to improper filtering of data passed to and retrieved from NVRAM. Data entered into the 'Router Name' input field through the web portal is submitted to apply.cgi as the value to the 'machine_name' POST parameter. When the 'preinit' binary receives the SIGHUP signal, it enters a code path that continues until it reaches offset 0x0042B5C4 in the 'start_lltd' function. Within the 'start_lltd' function, a 'nvram_get' call is used to obtain the value of the user-controlled 'machine_name' NVRAM entry. This value is then entered directly into a command intended to write the host name to a file and subsequently executed. Affected products include: Linksys E1200 Firmware, Linksys E2500 Firmware. Version information: Version 2.0.09.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.2 HIGH
AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionNVD

Devices in the Linksys ESeries line of routers (Linksys E1200 Firmware Version 2.0.09 and Linksys E2500 Firmware Version 3.0.04) are susceptible to OS command injection vulnerabilities due to improper filtering of data passed to and retrieved from NVRAM. Data entered into the 'Router Name' input field through the web portal is submitted to apply.cgi as the value to the 'machine_name' POST parameter. When the 'preinit' binary receives the SIGHUP signal, it enters a code path that continues until it reaches offset 0x0042B5C4 in the 'start_lltd' function. Within the 'start_lltd' function, a 'nvram_get' call is used to obtain the value of the user-controlled 'machine_name' NVRAM entry. This value is then entered directly into a command intended to write the host name to a file and subsequently executed.

Threat Intelligence Overview

EPSS Score
13.3%
Top 4% exploitable
Exploit
POC
Public exploit code exists
Data Quality
3 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC Yes
EPSS 13.3%
Patch available No
Active threat Yes
Deciding rule
HIGH severity + EPSS > 10%
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Out-of-Cycle
Exploitation· derived
Active
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
High

Priority Score

84
Low Medium High Critical
KEV: 0
EPSS: +13
CVSS: +36
PoC: +20
Weaponized: +15
Threat intel: 0
Gov advisory: 0

Attack Technique

OS command injection occurs when an application passes unsanitized user input directly into system shell commands.

Affected Products (CPE)NVD

cpe:2.3:o:linksys:e1200_firmware:2.0.09:*:*:*:*:*:*:*
cpe:2.3:o:linksys:e2500_firmware:3.0.04:*:*:*:*:*:*:*
CVE-2022-38555 CRITICAL POC
9.8 Aug 28

Linksys E1200 v1.0.04 is vulnerable to Buffer Overflow via ej_get_web_page_name. Rated critical severity (CVSS 9.8), thi

CVE-2025-60691 HIGH POC
8.8 Nov 13

A stack-based buffer overflow exists in the httpd binary of Linksys E1200 v2 routers (Firmware E1200_v2.0.11.001_us.tar.

CVE-2025-60690 HIGH POC
8.8 Nov 13

A stack-based buffer overflow vulnerability exists in the Linksys E1200 v2 router firmware that allows remote attackers

CVE-2025-60694 HIGH POC
7.5 Nov 13

A stack-based buffer overflow exists in the validate_static_route function of the httpd binary on Linksys E1200 v2 route

CVE-2025-60692 HIGH POC
8.4 Nov 13

A stack-based buffer overflow vulnerability exists in the libshared.so library of Cisco Linksys E1200 v2 routers (Firmwa

CVE-2018-3955 HIGH POC
7.2 Oct 17

An exploitable operating system command injection exists in the Linksys ESeries line of routers (Linksys E1200 Firmware

CVE-2018-3954 HIGH POC
7.2 Oct 17

Devices in the Linksys ESeries line of routers (Linksys E1200 Firmware Version 2.0.09 and Linksys E2500 Firmware Version

CVE-2025-60693 MEDIUM POC
6.5 Nov 13

A stack-based buffer overflow exists in the get_merge_mac function of the httpd binary on Linksys E1200 v2 routers (Firm

CVE-2025-60689 MEDIUM POC
5.4 Nov 13

An unauthenticated command injection vulnerability exists in the Start_EPI function of the httpd binary on Linksys E1200

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