CVE-2025-26399: SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerability

In short

SolarWinds Web Help Desk has a weakness classified as deserialization of untrusted data (CWE-502). CISA added it to its Known Exploited Vulnerabilities catalog on 2026-03-09. NVD lists CVSS 3.1 at 9.8 CRITICAL. CISA reports known ransomware campaign use.

What it is

“SolarWinds Web Help Desk contain a deserialization of untrusted data vulnerability in AjaxProxy that could allow an attacker to run commands on the host machine.” — CISA KEV, retrieved 2026-11-01

“SolarWinds Web Help Desk was found to be susceptible to an unauthenticated AjaxProxy deserialization remote code execution vulnerability that, if exploited, would allow an attacker to run commands on the host machine. This vulnerability is a patch bypass of CVE-2024-28988, which in turn is a patch bypass of CVE-2024-28986.” — NVD, retrieved 2026-11-01

Who is affected

SolarWinds Web Help Desk. NVD lists the following versions as affected:

• Versions through 12.8.6
• Versions version 12.8.7

Exploitation status

CISA KEV added: 2026-03-09. Known ransomware campaign use: Known (reported by CISA). Due date CISA set for US federal civilian agencies: 2026-03-12.

Scores

NVD CVSS 3.1: 9.8 CRITICAL; vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source [email protected].

EPSS by FIRST: 90.12%; percentile 99.80; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-502.

Timeline

CISA required action

“Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.” — CISA KEV

What to do

• Confirm whether you run SolarWinds Web Help Desk and which version.
• Apply the vendor update or mitigation in the advisory.
• Follow CISA’s required action.
• Review the vendor guidance on signs of compromise.
• Track the fix through completion.

References

• Release Notes: https://documentation.solarwinds.com/en/success_center/whd/content/release_notes/whd_12-8-7-hotfix-1_release_notes.htm
• Patch, Vendor Advisory: https://www.solarwinds.com/trust-center/security-advisories/CVE-2025-26399
• NVD detail
• CVE.org record
• CISA KEV catalog

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.