TL-MR6400 v5.3: Improper Neutralization of Special Elements used in an OS Command
CVE-2026-3841 is a high-severity improper neutralization of special elements used in an OS command vulnerability in TL-MR6400 v5.3 from TP-Link, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 1.9.0 Build 260108 as the first without the flaw, so updating TL-MR6400 v5.3 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 1.93% chance of exploitation within 30 days, higher than 80% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update TL-MR6400 v5.3 to 1.9.0 Build 260108 or a later version.
- Update Tl-mr6400 Firmware to 1.9.0 or a later version.
- Read the advisory on tp-link.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| TP-Link | TL-MR6400 v5.3 | before 1.9.0 Build 260108 | 1.9.0 Build 260108 |
| TP-Link | Tl-mr6400 Firmware | before 1.9.0 | 1.9.0 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.5 | High | CNA |
| CVSS 3.1 | 8.8 | High | NVD |
Official description
A command injection vulnerability has been identified in the Telnet command-line interface (CLI) of TP-Link TL-MR6400 v5.3. This issue is caused by insufficient sanitization of data processed during specific CLI operations. An authenticated attacker with elevated privileges may be able to execute arbitrary system commands. Successful exploitation may lead to full device compromise, including potential loss of confidentiality, integrity, and availability.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements used in an OS Command
The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.
How developers prevent this class of flaw
- If at all possible, use library calls rather than external processes to recreate the desired functionality.
- For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
More Improper Neutralization of Special Elements used in an OS Command vulnerabilities (CWE-78)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other references
Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities
- 9.8 Critical severity
- 9.9 Critical severity
- 9.8 Critical severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
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