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Weekly Signal
Live intelligence Updated 22 Aug 2026 · 21:24 UTC

SolarWinds · Serv-U

CVE-2021-35247

SolarWinds Serv-U Improper Input Validation Vulnerability

Recommended action

Confirm whether the technology is present and monitor for stronger exploitation evidence. Vendor advisory from www.solarwinds.com

View response plan
CVSS5.3
EPSS3.5%
KEVYes
ExploitationConfirmed exploitation
RemediationFixed release identified ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 3.5%; technical severity is CVSS 5.3.

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.

Who should care

  • Teams operating Serv-U
  • Vulnerability and exposure management teams
  • Security operations teams monitoring exploitation activity

Response plan

What I would do

  1. Confirm whether Serv-U is present in the environment.
  2. Identify affected versions and establish whether vulnerable services are exposed or reachable.
  3. Vendor advisory from www.solarwinds.com
  4. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Treatment intelligence

Remediation intelligence

Not yet verified

Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.

Verification noteAutomated link verification has not completed for this guidance yet.

Technical details

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CWE
CWE-20
Affected versions
SolarWinds Serv-U (End Excluding 15.3)
Fixed versions
SolarWinds Serv-U (Fixed from 15.3)
Published
10 January 2022
Attack vector
Network
Privileges required
None
User interaction
None

Signal timeline

  1. CVE published
  2. Added to CISA KEV
  3. Latest EPSS score: 3.5%
  4. Signal calculated at 64

External references

Live public intelligence This assessment combines public-source evidence. Validate the affected product, version and exposure against your own environment before making a risk decision.