Gl-s20 Firmware: Buffer Copy without Checking Size of Input
CVE-2023-31475 is a critical-severity buffer copy without checking size of input vulnerability in Gl-s20 Firmware from GL.iNet, with a CVSS 3.1 base score of 9.8 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 3.216 as the first without the flaw, so updating Gl-s20 Firmware to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 13.7% chance of exploitation within 30 days, which is in the top 3.43% of all scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Gl-s20 Firmware to 3.216 or a later version.
- Update Gl-x3000 Firmware to 3.216 or a later version.
- Update Gl-mt3000 Firmware to 3.216 or a later version.
- Read the advisory on gl-inet.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
Version data comes from NVD's product matching; 7 further products are omitted here. 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
- 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:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | NVD |
| CVSS 3.1 | 9.0 | Critical | CISA (ADP) |
Official description
An issue was discovered on GL.iNet devices before 3.216. The function guci2_get() found in libglutil.so has a buffer overflow when an item is requested from a UCI context, and the value is pasted into a char pointer to a buffer without checking the size of the buffer.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Buffer Copy without Checking Size of Input
The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
More Buffer Copy without Checking Size of Input vulnerabilities (CWE-120)
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
Advisories
Technical write-ups (may include proof of concept)
- github.com/gl-inet/CVE-issues/blob/main/3.215/Buffer_Overflow.mdExploit, Third Party Advisory
Other references
Other vulnerabilities in Gl-s20 Firmware
- 7.5 High severity
- 7.5 High severity
Recent Buffer Copy without Checking Size of Input vulnerabilities
- 7.8 High severity
- 8.8 High severity
- 8.1 High severity
- 7.1 High severity
- 7.8 High severity
- 8.8 High severity
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