Exploited CVEs / SolarWinds / CVE-2025-26399

CVE-2025-26399

SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted, and the vulnerability is known to be used in ransomware campaigns. Federal agencies were required to remediate by 2026-03-12 (that deadline has passed); treat that date as the outer bound for your own environment. Check the vendor security advisory for the fix.

CriticalCISA KEVRansomware

Actively exploited SolarWinds Web Help Desk vulnerability, Critical severity, CVSS 9.8. Added to the CISA KEV catalog 2026-03-09.

Senserva AI read on CVE-2025-26399 CISA required action Official fix for CVE-2025-26399 Admin questions #61 hottest CVE right now

Risk summary

CVSS base

9.8

EPSS exploit probability

88%

Severity

Critical

Added to KEV

2026-03-09

CISA due date

2026-03-12 (past due)

Senserva AI Opinion for CVE-2025-26399

SolarWinds Web Help Desk suffers a deserialization flaw in AjaxProxy that lets attackers run commands on the host, rated Critical at CVSS 9.8 with an 88% EPSS score and confirmed exploited since 2026-03-09. It is the third actively exploited flaw in this product within roughly a month, a pattern that says attackers are systematically working the codebase. Help desk platforms hold employee data and often privileged integration credentials.

Do this: Patch Web Help Desk to the latest build covering all three KEV flaws, or take it off the internet if you cannot patch today.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2025-26399

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2025-26399, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2025-26399.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2025-26399: SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerability
- Affected: SolarWinds Web Help Desk
- Severity: Critical, CVSS 9.8; EPSS 30-day exploitation probability 88%
- Added to CISA KEV: 2026-03-09; federal remediation due 2026-03-12
- Ransomware-linked: YES
- 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.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch immediately

Exploited in the wild and used in ransomware campaigns.

No vendor fix is mapped yet. This page refreshes daily and will name the patch the day one is published.

Do this now: Move this ahead of everything else in the queue, then verify the fix actually landed on every exposed device.

Updated August 7, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2025-26399

Published

2026-03-09

Last revised

2026-03-09

Changes tracked

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

What changed, and when

2026-03-09 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 9.8; EPSS first scored at 88.3%
2026-08-04 CVSS 9.8 to 0.0; linked to ransomware activity; CVSS 0.0 to 9.8

Recorded by Senserva from CISA KEV and FIRST EPSS on the dates shown. This is what moved and when, which neither NVD nor the vendor advisory publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2026-03-12 (past due).

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

Official fix for CVE-2025-26399

Check the vendor's security advisory channel for the patched Web Help Desk versions and workarounds.

CISA KEV entry

Common questions about CVE-2025-26399

Is CVE-2025-26399 actively exploited?

Yes. CVE-2025-26399 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2026-03-09, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 88%. CISA also reports it is known to be used in ransomware campaigns.

What is the CISA deadline and required action for CVE-2025-26399?

CISA set the federal (BOD 22-01) remediation due date at 2026-03-12, which has passed; treat any unremediated system as overdue. The verbatim 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.

What fixes CVE-2025-26399?

Check the vendor's security advisory for the patched Web Help Desk versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2025-26399?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2025-26399's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

More exploited SolarWinds CVEs

The newest SolarWinds entries on the CISA KEV catalog:

CVE-2026-28318 CVE-2025-40536 CVE-2025-40551 CVE-2024-28987 CVE-2024-28986 CVE-2024-28995 CVE-2021-35247 CVE-2020-10148

All SolarWinds exploited CVEs on one page: SolarWinds vulnerabilities actively exploited.

Authoritative references

CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.