CVE-2021-35247Known exploitationNetwork attack vector

LDAP input manipulation via unsanitized login characters

Published Jan 7, 2022 · Updated Oct 21, 2025

Improper input validation in SolarWinds Serv-U before 15.3 allows remote attackers to alter LDAP authentication input via crafted login characters. The web login input path forwards characters to LDAP authentication without sufficient validation or sanitization. LDAP servers ignored the improper characters in observed cases, and SolarWinds reported no downstream effect; user interaction is required.

CVSS severity5.3
Medium
EPSS probability3.45%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in SolarWinds Serv-U before 15.3 allows remote attackers to alter LDAP authentication input via crafted login characters. The web login input path forwards characters to LDAP authentication without sufficient validation or sanitization. LDAP servers ignored the improper characters in observed cases, and SolarWinds reported no downstream effect; user interaction is required.

The record

CVE
CVE-2021-35247
Published
Jan 7, 2022
Updated
Oct 21, 2025
Vendor
SolarWinds
Product
Serv-U
Classifications
CWE-20, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 7, 2022CVE publishedPublication date reported by the CVE source.
  2. Jan 21, 2022Exploitation reportedCISA Known Exploited Vulnerabilities Catalog listing
  3. Oct 21, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=15.2.5 and previous versions <15.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

SolarWinds · Serv-Uversion=15.2.5 and previous versions <15.3

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
4.3SolarWindsCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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