CVE-2025-26399

SolarWinds Web Help Desk insecure deserialization, confirmed exploited in the wild.

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.

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91%chance of exploitation in the next 30 days (EPSS), 99th percentile

9 Maradded to CISA's Known Exploited Vulnerabilities list, 2026

12 Marfederal remediation deadline, already passed

Passedpast the deadline: patch now

CISA's name for it	SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerability
Vendor and product	SolarWinds · Web Help Desk
Type	insecure deserialization · CWE-502
Exploited	Confirmed by CISA listed 9 March 2026
Likelihood	one of the most likely to be exploited of every vulnerability tracked
Deadline	12 March 2026 · already passed
Used in ransomware	Yes: CISA reports it used in ransomware campaigns
Advisories	www.solarwinds.com ↗ · documentation.solarwinds.com ↗ · nvd.nist.gov ↗

What to do

Three steps, in this order

Step 1

Apply the vendor's fix or mitigation; CISA lists only vulnerabilities seen exploited.

Step 2

If you cannot patch now, restrict network access to the affected product.

Step 3

Check for signs of compromise since the date it was added to the list.

CISA's 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.

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Questions

CVE-2025-26399 in short

Is CVE-2025-26399 being exploited?

Yes. CISA added CVE-2025-26399 to its Known Exploited Vulnerabilities catalogue on 9 March 2026, which it does only on evidence of exploitation in the wild.

What is the CISA deadline for CVE-2025-26399?

US federal agencies must remediate it by 12 March 2026. Everyone else should treat that date as the latest safe point to patch an internet-facing system.

How likely is CVE-2025-26399 to be exploited in the next 30 days?

FIRST's Exploit Prediction Scoring System gives it 91%, the 99th percentile of every CVE it scores.

How do I fix CVE-2025-26399?

Apply the vendor's fix or mitigation; CISA lists only vulnerabilities seen exploited. If you cannot patch now, restrict network access to the affected product. Check for signs of compromise since the date it was added to the list.

Same vendor

Other SolarWinds vulnerabilities being exploited

CVE	Product	Type	Listed
CVE-2026-28318	Serv-U	exploited vulnerability	5 June 2026
CVE-2025-40536	Web Help Desk	exploited vulnerability	12 February 2026
CVE-2025-40551	Web Help Desk	remote code execution	3 February 2026

Sources: CISA Known Exploited Vulnerabilities catalogue (released 10 November 2026) and FIRST EPSS. Page compiled automatically by SAK T.L.M, the threat-intelligence tool of SAK T.E.C, on 13 November 2026.