TEW-657BRM: Improper Neutralization of Special Elements used in a Command
CVE-2026-5355 is a high-severity improper neutralization of special elements used in a command vulnerability in TEW-657BRM from TRENDnet, 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. Affected TEW-657BRM versions: 1.00.1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 5.34% chance of exploitation within 30 days, which is in the top 7.25% of all scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of TEW-657BRM you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| TRENDnet | TEW-657BRM | 1.00.1 | Not stated |
| TRENDnet | Tew-657brm Firmware | 1.00.1 | Not stated |
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 | 2.1 | Low | CNA (vuldb.com) |
| CVSS 3.1 | 6.3 | Medium | CNA (vuldb.com) |
| CVSS 3.1 | 8.8 | High | NVD |
| CVSS 2.0 | 6.5 | Medium | CNA (vuldb.com) |
Official description
A vulnerability has been found in Trendnet TEW-657BRM 1.00.1. Affected by this issue is the function vpn_drop of the file /setup.cgi. The manipulation of the argument policy_name leads to os command injection. The attack is possible to be carried out remotely. The exploit has been disclosed to the public and may be used. The vendor confirms, that "[t]he product in question (...) has been discontinued and end of life since June 23, 2011, that is more than 14 years ago. We no longer provide support for this product, so we are not able to confirm the vulnerabilities. We will make an announcement on our website's product support page and notify customers who registered their products with us." This vulnerability only affects products that are no longer supported by the maintainer.
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 a Command
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when 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.
- If possible, ensure that all external commands called from the program are statically created.
- Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.
More Improper Neutralization of Special Elements used in a Command vulnerabilities (CWE-77)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- vuldb.com/submit/781569Third Party Advisory, VDB Entry
- vuldb.com/vuln/354708Third Party Advisory, VDB Entry
Technical write-ups (may include proof of concept)
- github.com/panda666-888/vuls/blob/main/trendnet/tew-657brm/vpn_drop.mdExploit, Third Party Advisory
Other references
- vuldb.com/vuln/354708/ctiPermissions Required, VDB Entry
Other vulnerabilities in TEW-657BRM
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
Recent Improper Neutralization of Special Elements used in a Command vulnerabilities
- 8.8 High severity
- 7.2 High severity
- 9.8 Critical severity
- 8.8 High severity
- 9.8 Critical severity
- 9.8 Critical severity
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