Captive Portal: NULL Pointer Dereference
CVE-2023-38313 is a high-severity NULL pointer dereference vulnerability in Captive Portal from openNDS, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 10.1.2 as the first without the flaw, so updating Captive Portal to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.96% chance of exploitation within 30 days, higher than 62% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Captive Portal to 10.1.2 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Opennds | Captive Portal | before 10.1.2 | 10.1.2 |
Version data comes from NVD's product matching. 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
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.
Official description
An issue was discovered in OpenNDS Captive Portal before 10.1.2. it has a do_binauth NULL pointer dereference that can be triggered with a crafted GET HTTP request with a missing client redirect query string parameter. Triggering this issue results in crashing openNDS (a Denial-of-Service condition). The issue occurs when the client is about to be authenticated, and can be triggered only when the BinAuth option is set. Affected OpenNDS Captive Portal before version 10.1.2 fixed infixed in OpenWrt master, OpenWrt 23.05 and OpenWrt 22.03 on28. August 2023 by updating OpenNDS to version 10.1.3.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: NULL Pointer Dereference
The product dereferences a pointer that it expects to be valid but is NULL.
How developers prevent this class of flaw
- For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
- Select a programming language that is not susceptible to these issues.
- Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
Other vulnerabilities in Captive Portal
- 7.5 High severity
- 7.5 High severity
- 9.8 Critical severity
- 7.5 High severity
Recent NULL Pointer Dereference vulnerabilities
- 9.8 Critical severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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