NR7101 firmware: Buffer Copy without Checking Size of Input
CVE-2022-43389 is a critical-severity buffer copy without checking size of input vulnerability in NR7101 firmware from Zyxel, 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. Affected NR7101 firmware versions: < V1.15(ACCC.3)C0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.66% chance of exploitation within 30 days, higher than 52% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Lte3202-m437 Firmware to 1.00\(abwf.1\)c0 or a later version.
- Update Lte3316-m604 Firmware to 2.00\(abmp.6\)c0 or a later version.
- Update Lte7480-m804 Firmware to 1.00\(abra.6\)c0 or a later version.
- Read the advisory on zyxel.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 |
|---|---|---|---|
| Zyxel | NR7101 firmware | < V1.15(ACCC.3)C0 | Not stated |
| Zyxel | Lte3202-m437 Firmware | before 1.00\(abwf.1\)c0 | 1.00\(abwf.1\)c0 |
| Zyxel | Lte3316-m604 Firmware | before 2.00\(abmp.6\)c0 | 2.00\(abmp.6\)c0 |
| Zyxel | Lte7480-m804 Firmware | before 1.00\(abra.6\)c0 | 1.00\(abra.6\)c0 |
| Zyxel | Lte7490-m904 Firmware | before 1.00\(abqy.5\)c0 | 1.00\(abqy.5\)c0 |
| Zyxel | Nebula Fwa510 Firmware | before 1.15\(acgd.3\)c0 | 1.15\(acgd.3\)c0 |
| Zyxel | Nebula Fwa710 Firmware | before 1.15\(acgc.3\)c0 | 1.15\(acgc.3\)c0 |
| Zyxel | Nebula Nr7101 Firmware | before 1.15\(accc.3\)c0 | 1.15\(accc.3\)c0 |
| Zyxel | Nr5103 Firmware | before 4.19\(abyc.3\)c0 | 4.19\(abyc.3\)c0 |
| Zyxel | Nr5103e Firmware | Not specified in the record | Not stated |
| Zyxel | Nr7102 Firmware | before 1.00\(abyd.2\)c0 | 1.00\(abyd.2\)c0 |
| Zyxel | Nr7103 Firmware | before 1.00\(accz.1\)c0 | 1.00\(accz.1\)c0 |
| Zyxel | Ep240p Firmware | Not specified in the record | Not stated |
| Zyxel | Pm7320-b0 Firmware | Not specified in the record | Not stated |
| Zyxel | Pmg5317-t20b Firmware | Not specified in the record | Not stated |
| Zyxel | Pmg5617ga Firmware | Not specified in the record | Not stated |
| Zyxel | Pmg5622ga Firmware | Not specified in the record | 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
- 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 | 8.6 | High | CNA (zyxel.com.tw) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
A buffer overflow vulnerability in the library of the web server in Zyxel NR7101 firmware prior to V1.15(ACCC.3)C0, which could allow an unauthenticated attacker to execute some OS commands or to cause denial-of-service (DoS) conditions on a vulnerable device.
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: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in NR7101 firmware
- 9.8 Critical severity
- 7.5 High severity
- 8.8 High severity
Recent Buffer Copy without Checking Size of Input vulnerabilities
- 7.8 High severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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