G103: Improper Neutralization of Special Elements used in a Command
CVE-2026-5339 is a high-severity improper neutralization of special elements used in a command vulnerability in G103 from Tenda, 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 G103 versions: 1.0.0.5. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 6.5% chance of exploitation within 30 days, which is in the top 6.13% of all scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of G103 you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Tenda | G103 | 1.0.0.5 | Not stated |
| Tenda | G103 Firmware | 1.0.0.5 | 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 | 2.0 | Low | CNA (vuldb.com) |
| CVSS 3.1 | 4.7 | Medium | CNA (vuldb.com) |
| CVSS 3.1 | 8.8 | High | NVD |
| CVSS 2.0 | 5.8 | Medium | CNA (vuldb.com) |
Official description
A vulnerability was detected in Tenda G103 1.0.0.5. The impacted element is the function action_set_net_settings of the file gpon.lua of the component Setting Handler. Performing a manipulation of the argument authLoid/authLoidPassword/authPassword/authSerialNo/authType/oltType/usVlanId/usVlanPriority results in command injection. It is possible to initiate the attack remotely. The exploit is now public and may be used.
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/781132Third Party Advisory, VDB Entry
- vuldb.com/submit/781133Third Party Advisory, VDB Entry
- vuldb.com/submit/781134Third Party Advisory, VDB Entry
- vuldb.com/submit/781135Third Party Advisory, VDB Entry
- vuldb.com/submit/781142Third Party Advisory, VDB Entry
- vuldb.com/submit/781143Third Party Advisory, VDB Entry
- vuldb.com/submit/781144Third Party Advisory, VDB Entry
- vuldb.com/submit/781145Third Party Advisory, VDB Entry
- vuldb.com/vuln/354670Third Party Advisory, VDB Entry
Technical write-ups (may include proof of concept)
- github.com/ZZ2266/.github.io/tree/main/Tenda%20G103/authLoidExploit, Third Party Advisory
Other references
- vuldb.com/vuln/354670/ctiPermissions Required, VDB Entry
- tenda.com.cn/Product
Other vulnerabilities in G103
- 7.2 High severity
Recent Improper Neutralization of Special Elements used in a Command vulnerabilities
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 9.8 Critical severity
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