Vulnerability report

Active exploitation observed Confirmed confidence Not in CISA KEV

CVE-2025-40553

Web Help Desk Deserialization

SolarWinds / Web Help Desk · 12.8.8 HF1 and below

Watch CVE-2025-40553 Browse KEV feed
Severity
CVSS 9.8 · Critical
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
68.0%
First observed
18 Aug 2026
Last observed
03 Oct 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2025-40553 is an unauthenticated vulnerability affecting SolarWinds Web Help Desk. SolarWinds Web Help Desk was found to be susceptible to an untrusted data deserialization vulnerability that could lead to remote...

Is it exploited?

Yes. Previdian sensors observed exploitation attempts with confirmed confidence.

Who is affected?

SolarWinds / Web Help Desk 12.8.8 hf1 and below.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

Web Help Desk Deserialization

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.

SolarWinds Affected
Web Help Desk
12.8.8 HF1 and below
Published
28 Jan 2026
Exploitation Reported
18 Aug 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

Previdian

Recorded 18 Aug 2026

Previdian independently recorded this as exploited after first seeing it in honeypot sensors.

Active exploitation observed

Previdian sensor

First observed 18 Aug 2026

Previdian first observed exploitation attempts targeting this vulnerability in our honeypot sensors.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
Previdian Sensors First 2026-09-01 12:15 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

First-party evidence of exploitation activity

Previdian sensors recorded exploitation attempts targeting this vulnerability. The cards and chart show volume, unique attackers, and daily activity.

35

Attempts observed

12

Unique attacker IPs

8

Attacker countries

CA · CN · DE · GB · IN · JP · SG · US

1

Sensors observed

CVE-2025-40553 exploitation attempts over the last 62 days

Daily events observed by Previdian sensors

Updated 17 Oct 2026

0
12
0
0
0
0
0
0
1
0
0
12
0
0
0
6
0
0
0
0
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
17 Aug 30 Aug 12 Sep 25 Sep 17 Oct

First observed 18 Aug 2026 · Last observed 03 Oct 2026

Pro adds sensor region and window summaries. Enterprise adds raw IPs, paths, User-Agents, and payloads.

Start 14-day Pro trial

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
1
1
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

Previdian virtual patch guidance is available for this CVE.

AWS WAF Cloudflare ModSecurity

Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

Learn about Pro API access

Virtual Patch Detail

Compensating WAF rules for this CVE.

Available

Enterprise feature. Virtual patch rule content and deployable vendor exports (ModSecurity, Cloudflare, AWS WAF) are available to Previdian Enterprise users.

Talk to Sales Learn About Virtual Patches

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.8 Critical

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

68.0%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Deserialization of Untrusted Data CWE-502

Timeline

From disclosure to observed exploitation

  1. 03:29 UTC

    Virtual patch available

    Compensating WAF rule available to block exploitation

  2. 11:49 UTC

    Indicators of compromise added (12)

    Indicators of compromise recorded

  3. 11:49 UTC

    Observed by Previdian sensors

    Evidence-backed exploitation signal

  4. 07:35 UTC

    CVE published

    Vulnerability disclosed publicly

  5. 08:01 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

Start 14-day Pro trial Read API docs
  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2025-40553

Sample API response 
{
  "cve_id": "CVE-2025-40553",
  "confidence": "Confirmed",
  "cvss_score": 9.8,
  "cvss_estimated": false,
  "epss_score": 0.67975,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 35, "sensors": 1 }
}