CVE-2021-35247 — SERV-U
MEDIUMCVE-2021-35247 is a medium-severity (CVSS 4.3) Improper Input Validation vulnerability in solarwinds serv-u. It is in CISA's Known Exploited Vulnerabilities catalog (added 2022-01-21) — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.
Serv-U web login screen to LDAP authentication was allowing characters that were not sufficiently sanitized. SolarWinds has updated the input mechanism to perform additional validation…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2022-01-21. Federal agencies were required to remediate by 2022-02-04.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-35247.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-35247 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Description
Serv-U web login screen to LDAP authentication was allowing characters that were not sufficiently sanitized. SolarWinds has updated the input mechanism to perform additional validation and sanitization. Please Note: No downstream affect has been detected as the LDAP servers ignored improper characters. To insure proper input validation is completed in all environments. SolarWinds recommends scheduling an update to the latest version of Serv-U.
Affected Products
serv-usolarwindsResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every solarwinds serv-u deployment and check each version against the affected-products list above.
Fix
Apply the solarwinds serv-u security patch or hotfix for CVE-2021-35247 on the affected version, following the vendor advisory for your exact build.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
Frequently Asked Questions
Is CVE-2021-35247 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.