Actively Exploited — CISA KEV

CVE-2025-40551: SolarWinds Web Help Desk Critical Vulnerability

Severity: Critical | CVSS 3.1: 9.8 | Published: 2026-01-28 | KEV Added: 2026-02-03

What is CVE-2025-40551?

SolarWinds Web Help Desk was found to be susceptible to an untrusted data deserialization vulnerability that could lead to remote code execution, which would allow an attacker to run commands on the host machine. This could be exploited without authentication.

Technical Analysis

Weakness Classification

This vulnerability is classified as CWE-502 — Deserialization of Untrusted Data. The application deserializes untrusted data without sufficient validation, which can lead to remote code execution, denial of service, or other attacks.

Attack Vector Breakdown

  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
  • Confidentiality: High
  • Integrity: High
  • Availability: High

Impact Analysis

This vulnerability is exploitable over the network, meaning any system reachable via the internet or internal network is potentially at risk without physical access. The attack complexity is low, requires no special privileges, and needs no user interaction — making it straightforward to exploit at scale. Successful exploitation can result in full confidentiality breach (complete data disclosure), complete integrity compromise (data modification or code execution), total availability loss (denial of service). The application deserializes untrusted data without sufficient validation, which can lead to remote code execution, denial of service, or other attacks.

Exploitation Probability (EPSS): 87.0% chance of exploitation in the next 30 days (99th percentile). This places the vulnerability in the highest risk tier — immediate action is critical.

Is CVE-2025-40551 being exploited?

Yes. CVE-2025-40551 is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, restricted to CVEs with confirmed active exploitation in the wild. CISA added this vulnerability on 2026-02-03. Inclusion in KEV triggers the patching mandate under BOD 22-01 for U.S. federal civilian agencies, with a remediation deadline of 2026-02-06.

How to fix CVE-2025-40551

Apply the security update issued by SolarWinds for Web Help Desk. If an immediate patch is not possible, consult the vendor advisory for mitigation guidance, restrict network exposure of the affected service, and monitor logs for indicators of exploitation. CISA's Known Exploited Vulnerabilities catalog requires U.S. federal agencies to remediate this vulnerability by the due date shown below under Binding Operational Directive 22-01. Private organizations should treat KEV entries as priority-one patches because active exploitation has been confirmed in the wild.

Related Vulnerabilities

Other actively exploited vulnerabilities affecting Web Help Desk or sharing the same weakness (CWE-502):

  • CVE-2025-26399 (Critical 9.8) [same product + same CWE] — SolarWinds Web Help Desk was found to be susceptible to an unauthenticated…
  • CVE-2025-40536 (High 8.1) [same product] — SolarWinds Web Help Desk was found to be susceptible to a security control…
  • CVE-2026-28318 (High 7.5) [same vendor] — SolarWinds Serv-U is susceptible to specially crafted POST requests that crash…
  • CVE-2026-45247 (Critical 9.8) [same CWE] — Mirasvit Full Page Cache Warmer for Magento 2 before version 1.11.12 contains…
  • CVE-2023-21529 (High 8.8) [same CWE] — Microsoft Exchange Server Remote Code Execution Vulnerability

Frequently asked questions

Is CVE-2025-40551 critical?

CVE-2025-40551 has a CVSS 3.1 base score of 9.8 — Critical severity. It should be treated as a priority patch, especially given the active exploitation confirmed by CISA.

Is CVE-2025-40551 being actively exploited?

Yes — CISA added CVE-2025-40551 to the Known Exploited Vulnerabilities catalog on 2026-02-03. Inclusion in KEV means CISA has confirmed in-the-wild exploitation.

How do I patch CVE-2025-40551?

Apply the security update from SolarWinds for Web Help Desk. Federal agencies must remediate by 2026-02-06 under BOD 22-01.

What type of vulnerability is CVE-2025-40551?

CVE-2025-40551 is classified under CWE-502 (Deserialization of Untrusted Data). The application deserializes untrusted data without sufficient validation, which can lead to remote code execution, denial of service, or other attacks.

What is the CVSS score for CVE-2025-40551?

CVE-2025-40551 has a CVSS 3.1 base score of 9.8, classifying it as Critical severity. The attack vector is Network, attack complexity is Low, and no privileges are required.