CVE-2021-22681
CVE-2021-22681 is a security flaw in Rockwell products. Attackers are using a flaw in Rockwell products. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 5 Mar 2026.[1]
Rockwell products 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. Rockwell has published a fix or advice.
Description
CISA calls it an insufficient protected credentials in Rockwell Multiple Products. In its words: “Multiple Rockwell products contain an insufficient protected credentials vulnerability. Studio 5000 Logix Designer software may allow a key to be discovered. This key is used to verify Logix controllers are communicating with Rockwell Automation design software. If successfully exploited, this vulnerability could allow an unauthorized application to connect with Logix controllers. To leverage this vulnerability, an unauthorized user would require network access to the controller.”[1]
The CVE record adds: “Rockwell Automation Studio 5000 Logix Designer Versions 21 and later, and RSLogix 5000 Versions 16 through 20 use a key to verify Logix controllers are communicating with Rockwell Automation CompactLogix 1768, 1769, 5370, 5380, 5480: ControlLogix 5550, 5560, 5570, 5580; DriveLogix 5560, 5730, 1794-L34; Compact GuardLogix 5370, 5380; GuardLogix 5570, 5580; SoftLogix 5800. Rockwell Automation Studio 5000 Logix Designer Versions 21 and later and RSLogix 5000: Versions 16 through 20 are vulnerable because an unauthenticated attacker could bypass this verification mechanism and authenticate with Rockwell Automation CompactLogix 1768, 1769, 5370, 5380, 5480: ControlLogix 5550, 5560, 5570, 5580; DriveLogix 5560, 5730, 1794-L34; Compact GuardLogix 5370, 5380; GuardLogix 5570, 5580; SoftLogix 5800.”[2]
The underlying weakness is CWE-522, in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Rockwell’s advisory has them[3]. CISA names the product as Rockwell Multiple Products.
Most families won’t have Rockwell products; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 5 Mar 2026, 1,828 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 26 Mar 2026 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 64%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Rockwell has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.”[1]
- Check whether you use it.Rockwell products 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 26 Mar 2026 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 9.8.[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 64%.[4] |
See also
Similar flaws
- CVE-2021-30116, Kaseya Virtual System/Server Administrator (VSA): information disclosure ·
- CVE-2020-29583, Zyxel products: use of hard-coded credentials ·
- CVE-2017-9248, Progress ASP.NET AJAX and Sitefinity: telerik UI for ASP.NET AJAX and sitefinity cryptographic weakness ·
Added the same day
- CVE-2023-43000, Apple devices: use-after-free ·
- CVE-2023-41974, Apple iOS and iPadOS: use-after-free ·
- CVE-2021-30952, Apple devices: integer overflow or wraparound ·
- CVE-2017-7921, Hikvision products: improper authentication ·
References
- ^ Cybersecurity and Infrastructure Security Agency. “Rockwell Multiple Products Insufficient Protected Credentials Vulnerability”. Known Exploited Vulnerabilities Catalog, added 5 Mar 2026.
- ^ National Institute of Standards and Technology. “CVE-2021-22681 Detail”. National Vulnerability Database, published 3 Mar 2021.
- ^ Rockwell. Advisories and fixes: support.rockwellautomation.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.636, percentile 99.2, 31 Oct 2026.
- CVE Program. “CVE-2021-22681”. 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.