CVE-2021-35247: in the CISA KEV catalogue
SolarWinds Serv-U Improper Input Validation Vulnerability. CISA added CVE-2021-35247 to the Known Exploited Vulnerabilities catalogue on 2022-01-21 with a default due date of 2022-02-04. Known ransomware campaign use: Unknown. Forensic triage flag: No.
SolarWinds Serv-U versions 15.2.5 and earlier contain an improper input validation vulnerability that allows attackers to build and send queries without sanitization. (CISA description)
- Vendor / product
- SolarWinds Serv-U
- CWE
- CWE-20
- CISA required action
- Apply updates per vendor instructions.
- EPSS
- 3.7%, percentile 89 (scored 2026-11-03)
EPSS puts about 3.7 in 100 odds (3.7%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 89% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.
Vendor and reference links (from CISA)
Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.
Frequently asked questions
Is CVE-2021-35247 in the CISA KEV catalogue?
Yes. CISA added CVE-2021-35247 (SolarWinds Serv-U Improper Input Validation Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2022-01-21. CISA's default due date for it is 2022-02-04.
Is CVE-2021-35247 used in ransomware attacks?
CISA marks known ransomware campaign use as Unknown for CVE-2021-35247. That means CISA lacks confirmation, not that ransomware groups do not use it.
What should I do about CVE-2021-35247?
CISA's required action: Apply updates per vendor instructions.
Sources
- CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
- FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
- NVD record for CVE-2021-35247