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CVE-2021-35247

5.3, medium Known exploited

SolarWinds Serv-U Improper Input Validation Vulnerability

NVD (opens in a new tab) CVE.org (opens in a new tab) CISA KEV catalogue (opens in a new tab)
CVSS
5.3, medium medium CVSS v3.1
EPSS, next 30 days
3% higher than 88.8% of scored CVEs
Exploitation
Confirmed in the wild
Published
10 Jan 20224 years ago

Known exploited

CISA added this to the Known Exploited Vulnerabilities Catalog on 21 Jan 2022. US federal agencies had to remediate by 4 Feb 2022, a deadline that has passed.

Required action. Apply updates per vendor instructions.

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.

Details

Vendor
SolarWinds
Product
Serv-U
Weakness
CWE-20 (opens in a new tab)
Status
Analyzed
Updated
17 Jun 2026
Assigner
psirt@solarwinds.com

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

References 3

Advisories 2

Other references 1

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other SolarWinds CVEs

Every SolarWinds CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2026-28318 SolarWinds Serv-U Uncontrolled Resource Consumption Vulnerability KEV EPSS 2% 7.5, high
  • CVE-2025-40536 SolarWinds Web Help Desk Security Control Bypass Vulnerability KEV EPSS 74% 9.8, critical
  • CVE-2025-40551 SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerability KEV EPSS 84% 9.8, critical
  • CVE-2025-26399 SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerability KEV EPSS 90% 9.8, critical
  • CVE-2024-28987 SolarWinds Web Help Desk Hardcoded Credential Vulnerability KEV EPSS 93% 9.1, critical
  • CVE-2024-28986 SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerability KEV EPSS 85% 9.8, critical
  • CVE-2024-28995 SolarWinds Serv-U Path Traversal Vulnerability KEV EPSS 100% 7.5, high
  • CVE-2021-35211 SolarWinds Serv-U Remote Code Execution Vulnerability KEV EPSS 91% 10, critical

Beyond this page

Is CVE-2021-35247 in your network?

This page tells you how dangerous CVE-2021-35247 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

CVE-2021-35247 is in the CISA catalogue of exploited vulnerabilities: attackers are already exploiting it.

  • EXYS7600 OCELOT

    Find it before attackers do

    Ocelot scans your network on a schedule and reports every vulnerability it finds by its CVE identifier, with its CVSS score and how many of your hosts are affected. A finding like CVE-2021-35247 comes with the devices to patch.

    Learn more about EXYS7600 OCELOT

  • EXYS7950 KONDRA

    Detect it if it's exploited

    Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.

    Learn more about EXYS7950 KONDRA
Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 17 Oct 2026, not the live upstream state.