Asuswrt-Merlin New Gen: Out-of-bounds Write
CVE-2022-26376 is a critical-severity out-of-bounds write vulnerability in Asuswrt-Merlin New Gen from Asuswrt-Merlin, 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 Asuswrt-Merlin New Gen versions: prior to 386.7. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.49% chance of exploitation within 30 days, higher than 75% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Asuswrt to 3.0.0.4.386_48706 or a later version.
- Update New Gen to 386.7 or a later version.
- Update Xt8 Firmware to 3.0.0.4.386_48706 or a later version.
- 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 |
|---|---|---|---|
| Asuswrt-Merlin | Asuswrt-Merlin New Gen | prior to 386.7 | Not stated |
| ASUS | Asuswrt | before 3.0.0.4.386_48706 | 3.0.0.4.386_48706 |
| Asuswrt-merlin | New Gen | before 386.7 | 386.7 |
| ASUS | Xt8 Firmware | before 3.0.0.4.386_48706 | 3.0.0.4.386_48706 |
| ASUS | Tuf-ax3000 V2 Firmware | before 3.0.0.4.386_48750 | 3.0.0.4.386_48750 |
| ASUS | Xd4 Firmware | before 3.0.0.4.386_48790 | 3.0.0.4.386_48790 |
| ASUS | Et12 Firmware | before 3.0.0.4.386_48823 | 3.0.0.4.386_48823 |
| ASUS | Gt-ax6000 Firmware | before 3.0.0.4.386_48823 | 3.0.0.4.386_48823 |
| ASUS | Xt12 Firmware | before 3.0.0.4.386_48823 | 3.0.0.4.386_48823 |
| ASUS | Rt-ax58u Firmware | before 3.0.0.4.386_48908 | 3.0.0.4.386_48908 |
| ASUS | Xt9 Firmware | before 3.0.0.4.388_20027 | 3.0.0.4.388_20027 |
| ASUS | Xd6 Firmware | before 3.0.0.4.386_49356 | 3.0.0.4.386_49356 |
| ASUS | Gt-ax11000 Pro Firmware | before 3.0.0.4.386_48996 | 3.0.0.4.386_48996 |
| ASUS | Gt-axe16000 Firmware | before 3.0.0.4.386_48786 | 3.0.0.4.386_48786 |
| ASUS | Rt-ax86u Firmware | before 3.0.0.4.386_49447 | 3.0.0.4.386_49447 |
| ASUS | Rt-ax68u Firmware | before 3.0.0.4.386_49479 | 3.0.0.4.386_49479 |
| ASUS | Rt-ax82u Firmware | before 3.0.0.4.386_49380 | 3.0.0.4.386_49380 |
| ASUS | Rt-ax56u Firmware | before 3.0.0.4.386_49559 | 3.0.0.4.386_49559 |
| ASUS | Rt-ax55 Firmware | before 3.0.0.4.386_49559 | 3.0.0.4.386_49559 |
| ASUS | Gt-ax11000 Firmware | before 3.0.0.4.386_49559 | 3.0.0.4.386_49559 |
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 | 9.8 | Critical | NVD |
| CVSS 3.0 | 5.3 | Medium | CNA (cisco.com) |
Official description
A memory corruption vulnerability exists in the httpd unescape functionality of Asuswrt prior to 3.0.0.4.386_48706 and Asuswrt-Merlin New Gen prior to 386.7.. A specially-crafted HTTP request can lead to memory corruption. An attacker can send a network request to trigger this vulnerability.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended 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.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Technical write-ups (may include proof of concept)
- talosintelligence.com/vulnerability_reports/TALOS-2022-1511Exploit, Third Party Advisory
Recent Out-of-bounds Write vulnerabilities
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
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