CVE-2020-5902
CVE-2020-5902 is a security flaw in F5 BIG-IP, equipment big companies use to route traffic to their websites and apps. Attackers can run their own code on F5 BIG-IP. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 3 Nov 2021, and says ransomware gangs have used it.[1]
F5 BIG-IP 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. F5 has published a fix or advice.
Description
CISA calls it a traffic management user interface (TMUI) remote code execution in F5 BIG-IP. In its words: “F5 BIG-IP Traffic Management User Interface (TMUI) contains a remote code execution vulnerability in undisclosed pages.”[1]
The CVE record adds: “In BIG-IP versions 15.0.0-15.1.0.3, 14.1.0-14.1.2.5, 13.1.0-13.1.3.3, 12.1.0-12.1.5.1, and 11.6.1-11.6.5.1, the Traffic Management User Interface (TMUI), also referred to as the Configuration utility, has a Remote Code Execution (RCE) vulnerability in undisclosed pages.”[2]
The underlying weakness is path traversal (CWE-22), 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; F5’s advisory has them[3]. CISA names the product as F5 BIG-IP.
Most families won’t have F5 BIG-IP; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 3 Nov 2021, 490 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 3 May 2022 to fix it.[1] CISA says ransomware gangs have used it.
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 over 99%. 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
F5 has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.F5 BIG-IP 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 3 May 2022 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, noting that ransomware gangs have used it.[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 over 99%.[4] |
See also
Other F5 BIG-IP flaws
- CVE-2025-53521: stack-based buffer overflow ·
- CVE-2022-1388: missing authentication ·
Other F5 flaws
- CVE-2026-94127, F5 BIG-IP APM: heap-based buffer overflow ·
- CVE-2023-46748, F5 BIG-IP Configuration Utility: SQL injection ·
- CVE-2023-46747, F5 BIG-IP Configuration Utility: authentication bypass ·
- CVE-2021-22991, F5 BIG-IP Traffic Management Microkernel: buffer overflow ·
- CVE-2021-22986, F5 BIG-IP and BIG-IQ Centralized Management: icontrol REST remote code execution ·
Other path traversal flaws
- CVE-2025-61624, Fortinet products: path traversal ·
- CVE-2021-3199, ONLYOFFICE Docs: server path traversal ·
- CVE-2026-104286, Fortinet FortiMail: path traversal ·
- CVE-2026-93616, Check Point products: path traversal ·
- CVE-2026-66384, JFrog Artifactory: improper limitation of a pathname to a restricted directory ·
Added the same day
- CVE-2021-42258, BQE BillQuick Web Suite: SQL injection ·
- CVE-2021-42013, Apache HTTP Server: path traversal ·
- CVE-2021-41773, Apache HTTP Server: path traversal ·
- CVE-2021-40539, Zoho ManageEngine: aDSelfService plus authentication bypass ·
- CVE-2021-40444, Microsoft MSHTML: remote code execution ·
Every F5 flaw on CISA’s list · Everything added in November 2021
References
- ^ Cybersecurity and Infrastructure Security Agency. “F5 BIG-IP Traffic Management User Interface (TMUI) Remote Code Execution Vulnerability”. Known Exploited Vulnerabilities Catalog, added 3 Nov 2021.
- ^ National Institute of Standards and Technology. “CVE-2020-5902 Detail”. National Vulnerability Database, published 1 Jul 2020.
- ^ F5. Advisories and fixes: support.f5.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 1.000, percentile 100.0, 31 Oct 2026.
- CVE Program. “CVE-2020-5902”. 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.