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SolarWinds Serv-U EUVDEUVD-2026-46290

| CVE-2026-28309 CRITICAL
Missing Authorization (CWE-862)
2026-07-21 SolarWinds GHSA-vv5r-rfhv-vx6x
9.1
CVSS 3.1 · Vendor: SolarWinds
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain domain administrator credentials
  2. Delivery
    Authenticate to Serv-U management interface
  3. Exploit
    Invoke account provisioning to create system admin
  4. Execution
    Gain persistent Serv-U system administrator control
  5. Impact
    Access or tamper with transferred files

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Authorization checks on every request
MITRE ATT&CK

1 technique across 1 tactic: Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires the attacker to already possess domain administrator privileges (consistent with CVSS PR:H) and network access to the Serv-U management interface; there is no user interaction required (UI:N). The specific abused capability is Serv-U's account-provisioning path, which fails to independently authorize creation of system administrator accounts and instead trusts the domain-admin role. Key limiting factors: this is not remotely exploitable by an unauthenticated or low-privileged attacker - the domain-admin prerequisite substantially narrows the threat population - and the vendor explicitly states the impact is lower in Windows deployments, so the realized severity depends on the deployment platform and how domain accounts are mapped to Serv-U privileges.

Impact

The provided CVSS 3.1 vector (AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H = 9.1) is driven largely by the scope change (S:C) and full impact triad, but the PR:H metric is the decisive real-world limiter: exploitation requires an attacker to already hold domain administrator privileges, which is itself among the most powerful positions in a Windows environment. This tempers the practical severity - an actor who is already domain admin has extensive control regardless - so this is better characterized as a lateral/persistence-and-consolidation risk (gaining a durable, application-level admin foothold in the MFT platform) than an initial-access break. No EPSS score, SSVC decision, KEV listing, or POC was provided; there is no public exploit identified at time of analysis, and nothing indicates active exploitation. The vendor's own statement that 'impact is lower in Windows deployments' conflicts somewhat with the uniform C:H/I:H/A:H rating and should be verified against the specific deployment platform. Net: a legitimately high-severity access-control defect worth prompt patching, but not an unauthenticated internet-facing emergency - the PR:H precondition means it is not automatable mass-exploitation.

Exploit ScenarioDerived

An insider or an attacker who has already compromised a domain administrator account logs into Serv-U and uses the account-management functionality to create a new Serv-U system administrator account, granting themselves persistent, application-level control over the file transfer platform and its stored/transiting data. This yields a durable admin foothold that survives remediation of the original domain compromise. No public exploit code has been identified at time of analysis, and given AV:N/AC:L the action is straightforward once the required domain-admin privileges are held.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Jul 21, 2026

Privilege escalation in SolarWinds Serv-U managed file transfer allows a user holding domain administrator privileges to create Serv-U system administrator accounts, crossing an authorization boundary the product is expected to enforce independently. Tracked as CVE-2026-28309 (CWE-862, Missing Authorization) and reported by SolarWinds, it carries a 9.1 CVSS due to scope change and full C/I/A impact, though the vendor notes the impact is lower in Windows deployments. There is no public exploit identified at time of analysis and it is not listed in CISA KEV.

RemediationAI

Upgrade to the fixed Serv-U 2026-3 release, which is the version referenced in the vendor release notes (https://documentation.solarwinds.com/en/success_center/servu/content/release_notes/servu_2026-3_release_notes.htm); confirm the exact patched build against the SolarWinds security advisory at https://www.solarwinds.com/trust-center/security-advisories/CVE-2026-28309. Because exploitation requires domain administrator privileges, the strongest compensating control until patching is to tightly restrict and monitor domain admin group membership and to decouple Serv-U system-administrator provisioning from domain-admin identities - review and prune existing Serv-U system administrator accounts, and audit account-creation events for unexpected new admins (trade-off: added administrative overhead and possible disruption to automated provisioning). Where feasible, limit which directory groups are trusted for Serv-U administrative mapping and enable logging/alerting on privileged account creation. No effective network-layer workaround exists because the flaw is in application authorization logic, not a specific port or endpoint, so patching is the durable fix.

Affected VersionsENISA

Serv-U 15.5.4 HF1 and below

Affects your stack

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Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Serv-U is SolarWinds' managed file transfer (MFT) and secure file server product (CPE cpe:2.3:a:solarwinds:serv-u), commonly fronting FTP/FTPS/SFTP/HTTPS file exchange for enterprises. The root cause is CWE-862 Missing Authorization: the account-provisioning logic conflates an external directory role (domain administrator) with the application's own privileged role (Serv-U system administrator), so a domain admin identity is permitted to mint top-tier Serv-U admin accounts without a separate authorization check inside the product. This is an access-control/authentication-bypass flaw (per the vendor tags 'Authentication Bypass', 'Serv U', 'Microsoft') rather than a memory-safety or injection bug; the trust boundary between directory-level administration and application-level administration is not properly segregated. The vendor's note that impact is 'lower in Windows deployments' suggests platform-specific differences in how domain accounts map to Serv-U privileges.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (SolarWinds) PRIMARY 9.1 CRITICAL
AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
vuln.today AI 9.1 CRITICAL

Requires pre-existing domain admin (PR:H) over the network with no user interaction; creating a Serv-U system admin crosses an authorization boundary (S:C) yielding full C/I/A over the platform.

3.1 AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Primary rating from Vendor (SolarWinds).

CVSS VectorVendor: SolarWinds

Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

DescriptionCVE.org

SolarWinds Serv-U is affected by a broken access control vulnerability that allows a domain administrator to create system administrator accounts. The impact is lower in Windows deployments.

Executive ViewAI

Why It Matters

SolarWinds Serv-U managed file transfer solution contains a critical privilege escalation vulnerability (CVE-2026-28309, CVSS 9.1) that enables domain administrators to create unauthorized Serv-U system administrator accounts, potentially compromising enterprise file transfer security and data integrity. No patch is currently available and no public exploit code has been identified; however, this represents a significant insider threat requiring immediate access control review and compensating controls.

Business Impact: Severe
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations: (1) Implement strict role-based access control separating domain administrator and Serv-U administrator functions; (2) Enable comprehensive audit logging for all Serv-U administrative activities, account creation, and configuration changes; (3) Deploy network segmentation limiting domain administrator access to Serv-U management interfaces; (4) Establish baseline inventory and monitoring of Serv-U administrative accounts to detect unauthorized creation; (5) Increase frequency of Serv-U access reviews and approval workflows.

Threat Intelligence Overview

EPSS Score
0.3%
Top 73% exploitable
Prevalence
Medium
Enterprise managed file transfer product, common but not universally deployed
Social Media
1
Sightings
Data Quality
4 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact
Very High

Priority Score

46
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +46
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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