CVE-2020-24355

Name: CVE-2020-24355
Creator: NVD / NIST
Published: 2020-09-02T12:15:10.55+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 2.18%

Last modified Jun 17, 2026

CVE-2020-24355 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Zyxel VMG5313-B30B router on firmware 5.13(ABCJ.6)b3_1127, and possibly older versions of firmware are affected by insecure permissions which allows regular and other users to create new users with elevated privileges. This is done by changing "FirstIndex" field in JSON that is POST-ed during account creation. EPSS estimates a 2.18% chance of exploitation in the next 30 days.

Description

Zyxel VMG5313-B30B router on firmware 5.13(ABCJ.6)b3_1127, and possibly older versions of firmware are affected by insecure permissions which allows regular and other users to create new users with elevated privileges. This is done by changing "FirstIndex" field in JSON that is POST-ed during account creation. Similar may also be possible with account deletion.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

2.18%

80.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-732

Affected Software

Vendor	Product	Versions
Zyxel	Vmg5313-B30b Firmware	<= 5.13\(abcj.6\)b3_1127

References

https://blog.somegeneric.ninja/Zyxel_VMG5153_B30BExploit, Third Party Advisory
https://blog.somegeneric.ninja/Zyxel_VMG5153_B30B_part2Exploit, Third Party Advisory
https://www.zyxel.com/support/security_advisories.shtmlVendor Advisory
https://blog.somegeneric.ninja/Zyxel_VMG5153_B30BExploit, Third Party Advisory
https://blog.somegeneric.ninja/Zyxel_VMG5153_B30B_part2Exploit, Third Party Advisory
https://www.zyxel.com/support/security_advisories.shtmlVendor Advisory

Timeline

Published: Sep 2, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-24355?

How severe is CVE-2020-24355?

CVE-2020-24355 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 2.18% probability of exploitation in the next 30 days.

How do I fix CVE-2020-24355?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-24355?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST