Security Digest · Vulnerability record · Known exploited
CVE-2025-26399: SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerability
Exploited in the wild (CISA KEV). 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.
CISA KEV · added 2026-03-09 CVSS 9.8 Critical EPSS 90.1% · p99.8
Should you act?
Exploited: patch now if you run it
CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Yes, if you run SolarWinds Web Help Desk. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-03-09, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-03-12; treat that as the outer limit, not the target. CISA also lists it as known to be used in ransomware campaigns.
- EPSS 90.1%, percentile 99.8: FIRST’s model estimates a 90.1% chance of exploitation activity in the next 30 days, higher than 99.8% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
What it is
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.
CISA’s summary
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.
Weakness type: CWE-502.
Product: SolarWinds Web Help Desk · Assigned by: SolarWinds · Published: 2025-09-23
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| SolarWinds | Web Help Desk | 12.8.7 and below |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| SolarWinds | 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: added 2026-03-09; federal due date 2026-03-12. Known ransomware use: Known.
- 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 SSVC assessment: exploitation active, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 90.12% probability of exploitation activity in the next 30 days; percentile 99.8.
Timeline
- — CVE record published by SolarWinds
- — Added to CISA’s Known Exploited Vulnerabilities catalog
- — CISA remediation deadline for US federal agencies
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- Listed in CISA KEV notes (solarwinds.com) solarwinds.com
- Listed in CISA KEV notes (documentation.solarwinds.com) documentation.solarwinds.com
Vulnerability records
- CVE.org record CVE-2025-26399 cve.org
- NVD entry CVE-2025-26399 nvd.nist.gov
Government
Other references from the CVE record and advisory
- solarwinds.com solarwinds.com
- microsoft.com microsoft.com
All exploited SolarWinds vulnerabilities · Today’s Security Digest