How severe is CVE-2021-35247?

CVE-2021-35247 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2021-35247 being actively exploited?

Yes. CVE-2021-35247 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2022-01-21, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2021-35247?

CVE-2021-35247 affects Solarwinds Serv-u. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-35247?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2021-35247 have an EU (EUVD) identifier?

Yes. CVE-2021-35247 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-21890. It is also flagged as exploited in the EUVD (since 2022-01-21).

When was CVE-2021-35247 published?

CVE-2021-35247 was published on 2022-01-10 and last updated on 2026-06-17.

CVE-2021-35247

CVE-2021-35247 is a medium-severity vulnerability in Solarwinds Serv-u with a CVSS 3.x base score of 4.3. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2022-01-21). The underlying weakness is classified as CWE-20.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
CVSS v2: 5.0
EPSS exploit prediction: 3% (87th percentile)
Actively exploited: Yes — listed in CISA KEV (added 2022-01-21)
EU (EUVD) id: EUVD-2021-21890
EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2022-01-21)
Weakness: CWE-20
Affected product: Solarwinds Serv-u
Published: 2022-01-10
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-35247?: 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.
How severe is CVE-2021-35247?: CVE-2021-35247 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2021-35247 being actively exploited?: Yes. CVE-2021-35247 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2022-01-21, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2021-35247?: CVE-2021-35247 affects Solarwinds Serv-u. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-35247?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2021-35247 have an EU (EUVD) identifier?: Yes. CVE-2021-35247 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-21890. It is also flagged as exploited in the EUVD (since 2022-01-21).
When was CVE-2021-35247 published?: CVE-2021-35247 was published on 2022-01-10 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:solarwinds:serv-u:*:*:*:*:*:*:*:*

More vulnerabilities in Solarwinds Serv-u

CVE-2020-35481 — Critical (CVSS 9.8): SolarWinds Serv-U before 15.2.2 allows Unauthenticated Macro Injection.
CVE-2025-40541 — Critical (CVSS 9.1): An Insecure Direct Object Reference (IDOR) vulnerability exists in Serv-U, which when exploited, gives a malicious…
CVE-2025-40540 — Critical (CVSS 9.1): A type confusion vulnerability exists in Serv-U which when exploited, gives a malicious actor the ability to execute…
CVE-2025-40539 — Critical (CVSS 9.1): A type confusion vulnerability exists in Serv-U which when exploited, gives a malicious actor the ability to execute…
CVE-2025-40538 — Critical (CVSS 9.1): A broken access control vulnerability exists in Serv-U which when exploited, gives a malicious actor the ability to…
CVE-2025-40549 — Critical (CVSS 9.1): A Path Restriction Bypass vulnerability exists in Serv-U that when abused, could give a malicious actor with access to…

All CVEs affecting Solarwinds Serv-u →

Other CWE-20 (Improper Input Validation) vulnerabilities

CVE-2026-48316 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48281 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48277 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48055 — Critical (CVSS 10.0): Streambert is a cross-platform Electron Desktop App to stream and download any video media. In versions 2.4.0 and…
CVE-2026-34910 — Critical (CVSS 10.0): A malicious actor with access to the network could exploit an Improper Input Validation vulnerability found in UniFi OS…
CVE-2026-33587 — Critical (CVSS 10.0): Lack of user input sanitisation in Open Notebook v1.8.3 allows the application user to execute Python code (and…

Browse all CWE-20 (Improper Input Validation) vulnerabilities →