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CVE-2023-39239· NVD / CVE Program· CNA twcert

ASUS RT-AX55、RT-AX56U_V2、RT-AC86U - Format String - 2

It is identified a format string vulnerability in ASUS RT-AX56U V2’s General function API. This vulnerability is caused by lacking validation for a specific value within its apply.cgi module. A remote attacker with administrator privilege can exploit this vulnerability to perform remote arbitrary code execution, arbitrary system operation or disrupt service.

HighCVSS 7.2 · v3.1—No exploit No fix recorded
Published
Sep 7, 2023
Updated
Jun 17, 2026
EPSS
1.3% · 69th percentile
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Report tools

JSON

Action score

28

Monitor

Low priority for now.

CVSS
28 / 40 · 7.2 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · twcert
7.2
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

VendorProduct
asusrt-ax55 firmware
asusrt-ax55
asusrt-ax56u v2 firmware
asusrt-ax56u v2
asusrt-ac86u firmware
asusrt-ac86u

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • asus rt-ac86u firmware3.0.0.4_386_51529
  • asus rt-ax55 firmware3.0.0.4.386_50460
  • asus rt-ax56u v2 firmware3.0.0.4.386_50460

Versions reported by the vendor

Affected version ranges reported by the assigning authority (twcert). Independent of NVD's CPE analysis and usually ahead of it.

  • ASUS RT-AC86U

    • 3.0.0.4_386_51529affected

  • ASUS RT-AX55

    • 3.0.0.4.386_50460affected

  • ASUS RT-AX56U_V2

    • 3.0.0.4.386_50460affected

Same product

asus: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-39780On ASUS RT-AX55 3.0.0.4.386.51598 devices, authenticated attackers can perform OS command injection via the /start_apply.htm qos_bw_rulelistKEV
    77This week
  • CVE-2023-41348ASUS RT-AX55 - command injection - 4
    35Monitor
  • CVE-2023-41347ASUS RT-AX55 - command injection - 3
    35Monitor
  • CVE-2023-41346ASUS RT-AX55 - command injection - 2
    35Monitor
  • CVE-2023-41345ASUS RT-AX55 - command injection - 1
    35Monitor
  • CVE-2023-39240ASUS RT-AX55、RT-AX56U_V2 - Format String - 3
    28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • Administrator privileges are required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
High
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-134 · Use of Externally-Controlled Format String

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

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Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records