CISA KEV Critical Insecure deserialization

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

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.

Published Sep 23, 2025 · Updated Oct 13, 2026 · Sources: CISA Known Exploited Vulnerabilities, NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: SolarWinds

Urgent

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

CISA KEV · Mar 9, 2026 R used by ransomware (CISA) Detection templates (Nuclei) · 1 Proofs of concept on GitHub · 1

How the score was calculated

Confirmed exploitation (CISA KEV)+35
Used in ransomware campaigns (CISA)+10
Public exploit/PoC (nuclei, github)+10
EPSS 89.5% (30-day exploitation probability)+15
Technical severity (critical)+10
Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Confirmed

CISA KEV, listed Mar 9, 2026

EPSS FIRST

89.5%

ahead of 100% of scored CVEs · Oct 15, 2026

Affects

Solarwinds

Web Help Desk

CVSS base

9.8

Critical · 4 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Active

none · proof-of-concept · active

Automatable

Yes

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented patch — www.solarwinds.com (NIST National Vulnerability Database)

CISA required action CISA

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

US federal deadline: Mar 12, 2026 — passed 218 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Solarwinds Web Help Desk).
Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
Apply the fixed version or the patch documented under Remediation.
EPSS ahead of 100% of scored CVEs: prioritize it in the patch queue.
Search available logs for exploit probes matching the vulnerability class (insecure deserialization), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Solarwinds	Web Help Desk	≤ 12.8.6version 12.8.7	Vulnerable	NIST National Vulnerability Database
Solarwinds	Web Help Desk	version 12.8.7 and below	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
9.8	CVSS 3.1	Critical	3.9	5.9	psirt@solarwinds.com via NIST National Vulnerability Database
9.8	CVSS 3.1	Critical	3.9	5.9	nvd@nist.gov via NIST National Vulnerability Database
9.8	CVSS 3.1	Critical	—	—	GitHub, Inc. via GitHub Security Advisories
9.8	CVSS 3.1	Critical	—	—	SolarWinds via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-502 · Deserialization of Untrusted Data

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

Listed

Mar 9, 2026

Federal deadline

Mar 12, 2026

passed 218 day(s) ago

Ransomware use

Known

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

Public exploits, PoCs and detection templates

Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.

Detection templates (Nuclei)

SolarWinds Web Help Desk < 12.8.7 - AjaxProxy Deserialization RCE

Proofs of concept on GitHub

Detection for CVE-2025-26399 ★ 2 Sep 23, 2025

Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.

EPSS over time FIRST

Oct 12, 2026 → Oct 15, 2026 · 4 reading(s) · max 89.50%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Monitor serialized objects in requests and unexpected processes spawned by the runtime.
Hunt retroactively in logs from before Mar 9, 2026 (KEV listing): exploitation may have started earlier.

web/proxy/WAF logsnetwork IDS/IPSendpoint telemetry (EDR)application logs

Timeline

What happened to this CVE, newest first.

2026
Affected products added · solarwinds/web help desk
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
Fix documented
Oct 13, 2026 · NIST National Vulnerability Database
Affected products added · solarwinds/web help desk
Oct 13, 2026 · NIST National Vulnerability Database
CVSS changed · 9.8
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Added to CISA KEV (detected)
Oct 13, 2026 · CISA Known Exploited Vulnerabilities
Record created in this database
Oct 13, 2026 · CISA Known Exploited Vulnerabilities
Added to CISA KEV catalog
Mar 8, 2026 · CISA
2025
CVE published
Sep 23, 2025 · SolarWinds

Source activity

Repeated readings are counted rather than listed.

2× References added · Oct 13, 2026 – Oct 13, 2026
1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

7 on the record

www.solarwinds.com/trust-center/security-advisories/CVE-2025-26399
Patch, Vendor Advisory, NIST National Vulnerability Database
www.cisa.gov/known-exploited-vulnerabilities-catalog
US Government Resource, NIST National Vulnerability Database
github.com/advisories/GHSA-vfrj-f292-3f24
GitHub Security Advisories
nvd.nist.gov/vuln/detail/CVE-2025-26399
GitHub Security Advisories
documentation.solarwinds.com/en/success_center/whd/content/release_notes/whd_12-8-7-hotfix-1_relea
Release Notes, NIST National Vulnerability Database
www.microsoft.com/en-us/security/blog/2026/02/06/active-exploitation-solarwinds-web-hel
GitHub Security Advisories
www.microsoft.com/en-us/security/blog/2026/02/06/active-exploitation-solarwinds-web-hel
Third Party Advisory, NIST National Vulnerability Database

Elsewhere on this site

Solarwinds
every CVE for this vendor

2026-03
what else CISA listed that month

Insecure deserialization
same class

CWE-502
other pages naming this weakness

Related CVEs (same products)

Critical CVE-2026-28323 SolarWinds Web Help Desk SAML Authentication Bypass Vulnerability Jul 30, 2026
High CVE-2026-28299 SolarWinds Web Help Desk Denial-of-Service Vulnerability Jun 2, 2026
Critical CVE-2025-40551 SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerability KEV Jan 28, 2026
High CVE-2025-40537 SolarWinds Web Help Desk Hardcoded Credentials Vulnerability Jan 28, 2026
Critical CVE-2025-40552 SolarWinds Web Help Desk Authentication Bypass (CVE-2025-40552) Jan 28, 2026
Critical CVE-2025-40553 SolarWinds Web Help Desk: untrusted data deserialization leading to RCE Jan 28, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-26399 is "SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerability", rated Critical. It affects Web Help Desk (Solarwinds); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 9.8 describes technical severity. EPSS 89.50% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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