CVE-2024-20399
CVE-2024-20399 is a security flaw in Cisco NX-OS, Cisco’s business networking equipment. Someone who already has a way in can use Cisco NX-OS to run their own code. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 2 Jul 2024.[1]
Cisco NX-OS is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Cisco has published a fix or advice.
Description
CISA calls it a command injection in Cisco NX-OS. In its words: “Cisco NX-OS contains a command injection vulnerability in the command line interface (CLI) that could allow an authenticated, local attacker to execute commands as root on the underlying operating system of an affected device.”[1]
The CVE record adds: “A vulnerability in the CLI of Cisco NX-OS Software could allow an authenticated user in possession of Administrator credentials to execute arbitrary commands as root on the underlying operating system of an affected device. This vulnerability is due to insufficient validation of arguments that are passed to specific configuration CLI commands. An attacker could exploit this vulnerability by including crafted input as the argument of an affected configuration CLI command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system with the privileges of root. Note: To successfully exploit this vulnerability on a Cisco NX-OS device, an attacker must have Administrator credentials. The following Cisco devices already allow administrative users to access the underlying operating system through the bash-shell feature,…”[2]
The underlying weakness is OS command injection (CWE-78), in MITRE’s list of common software weaknesses.
It scores 6.7 out of 10 on the Common Vulnerability Scoring System, which rates it medium, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Cisco’s advisory has them[3]. CISA names the product as Cisco NX-OS.
Most families won’t have Cisco NX-OS; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 2 Jul 2024, within a day of it being made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 23 Jul 2024 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 4%. That’s in the top 9% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Cisco has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”[1]
- Check whether you use it.Cisco NX-OS is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 23 Jul 2024 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 6.7.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 4%.[4] |
See also
Other Cisco flaws
- CVE-2026-76418, Cisco Secure Firewall ASA Software and Cisco Secure FTD Software: unchecked return value to NULL pointer dereference ·
- CVE-2026-76519, Cisco Secure Email Gateway: relative path traversal ·
- CVE-2026-76504, Cisco Catalyst SD-WAN Manager: hex encoding ·
- CVE-2026-76460, Cisco Identity Services Engine: incorrect use of privileged APIs ·
- CVE-2026-76461, Cisco Secure Email Gateway: SQL injection ·
Other OS command injection flaws
- CVE-2026-110447, Collabora Online – Built-in CODE Server: online – built-in CODE server OS command injection ·
- CVE-2026-106931, EG Secure Solutions SiteGuard Server Edition: OS command injection ·
- CVE-2026-83549, SonicWall SMA1000 Appliances: OS command injection ·
- CVE-2026-49869, Kestra OSS: OSS OS command injection ·
- CVE-2026-73570, Synacor Zimbra Collaboration Suite (ZCS): OS command injection ·
Every Cisco flaw on CISA’s list · Everything added in July 2024
References
- ^ Cybersecurity and Infrastructure Security Agency. “Cisco NX-OS Command Injection Vulnerability”. Known Exploited Vulnerabilities Catalog, added 2 Jul 2024.
- ^ National Institute of Standards and Technology. “CVE-2024-20399 Detail”. National Vulnerability Database, published 1 Jul 2024.
- ^ Cisco. Advisories and fixes: sec.cloudapps.cisco.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.043, percentile 91.2, 31 Oct 2026.
- CVE Program. “CVE-2024-20399”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.