NSClient++: Improper Control of Generation of Code
CVE-2025-34079 is a high-severity improper control of generation of code vulnerability in NSClient++, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. Affected NSClient++ versions: 0.5.2.35. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.7% chance of exploitation within 30 days, higher than 78% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of NSClient++ you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| NSClient++ | NSClient++ | 0.5.2.35 | 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
- LocalThe attacker needs local access or must trick a user into running something.
- 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:L/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 | 7.5 | High | CNA (vulncheck.com) |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
An authenticated remote code execution vulnerability exists in NSClient++ version 0.5.2.35 when the web interface and ExternalScripts module are enabled. A remote attacker with the administrator password can authenticate to the web interface (default port 8443), inject arbitrary commands as external scripts via the /settings/query.json API, save the configuration, and trigger the script via the /query/{name} endpoint. The injected commands are executed with SYSTEM privileges, enabling full remote compromise. This capability is an intended feature, but the lack of safeguards or privilege separation makes it risky when exposed to untrusted actors.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Control of Generation of Code
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
How developers prevent this class of flaw
- Refactor your program so that you do not have to dynamically generate code.
- Run your code in a jail or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which code can be executed by your product. Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
- Use dynamic tools and techniques that interact with the product using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The product's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
More Improper Control of Generation of Code vulnerabilities (CWE-94)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Technical write-ups (may include proof of concept)
- raw.githubusercontent.com/rapid7/metasploit-framework/master/modules/exploits/windows/http/nscp_authenticated…Exploit
- vulncheck.com/advisories/nsclient-localtoremote-system-compromiseExploit, Third Party Advisory
- exploit-db.com/exploits/48360Exploit, VDB Entry
Other vulnerabilities in NSClient++
- 7.8 High severity
Recent Improper Control of Generation of Code vulnerabilities
- 9.4 Critical severity
- 9.1 Critical severity
- 8.8 High severity
- 8.6 High severity
- 9.8 Critical severity
- 7.8 High severity
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