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Citrix UniconOS EUVDEUVD-2026-100753

| CVE-2026-53563 MEDIUM
OS Command Injection (CWE-78)
2026-10-13 secure@citrix.com GHSA-jq59-m47r-c584
6.9
CVSS 4.0 · Vendor: citrix
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Attack ChainAIDerived

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

  1. Access
    Obtain local low-privileged access to UniconOS endpoint
  2. Exploit
    Invoke vulnerable OS component
  3. Execution
    Trigger persistent command execution
  4. Impact
    Read sensitive data / retain foothold

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization OS command sanitization, avoid shell exec
MITRE ATT&CK

2 techniques across 1 tactic: Execution

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

Exploitation Conditions

Exploitation requires LOCAL access to a device running Citrix UniconOS with at least low-privilege authenticated access (AV:L/PR:L), and no user interaction is needed (UI:N). It is NOT remotely exploitable over the network, which is the primary limiting factor - an attacker must already have a foothold or valid low-privilege credentials on the endpoint. Affected deployments are UniconOS versions before 2607.2 CR and before 2603 LTSR CU2; systems patched to those versions are not exploitable. The description does not name a specific optional feature or non-default setting, so the condition is possession of local low-privileged access to an unpatched UniconOS device rather than a particular configuration toggle.

Impact

This is a moderate-risk, locally-exploitable issue rather than an urgent widespread threat. The vendor-supplied CVSS 4.0 vector (AV:L/AC:L/AT:N/PR:L/UI:N) indicates a LOCAL attack vector with LOW complexity and LOW privileges required but NO user interaction, yielding a MEDIUM base score of 6.9. There is no EPSS score, no CISA KEV listing, and no public exploit code supplied in the intelligence, so exploitation probability signals are absent - this is not confirmed as actively exploited. The impact profile is notable for internal inconsistency: the CVSS declares HIGH confidentiality impact (VC:H) with only LOW integrity and availability (VI:L/VA:L), and the input Tags label this 'Information Disclosure', yet the CVE title describes 'Persistent Command Execution', which would normally imply high integrity/availability impact - this disagreement should be verified with Citrix before final triage. Because the vector is local and requires authenticated low-privilege access, this is better treated as a post-compromise privilege/persistence or data-exposure concern on affected endpoints than as a remotely wormable priority; the local AV meaningfully caps real-world exposure despite the 'command execution' framing.

Exploit ScenarioDerived

A low-privileged user already able to log in to or run code on a Citrix UniconOS thin-client endpoint abuses the flaw to execute commands that persist on the device and/or to read data they should not be able to access. Because the vector is local (AV:L) with low privileges (PR:L) and no user interaction, the attacker needs an existing foothold on the device rather than network reach. No public exploit identified at time of analysis.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 14, 2026

Persistent command execution in Citrix UniconOS lets a locally authenticated low-privilege user plant commands that survive normal operation and execute in a privileged context, giving the attacker sustained access to data and code on the endpoint. The flaw affects UniconOS releases before 2607.2 CR and before 2603 LTSR CU2; it is not remotely exploitable and requires an existing foothold or valid low-privilege credentials on the device, with no user interaction needed. No public exploit code has been identified at time of analysis, no confirmed active exploitation (CISA KEV) has been reported, and the vendor has released a patch, making this a moderate-risk, locally-scoped issue rather than an urgent widespread threat.

RemediationAI

Vendor-released patch is available: upgrade Citrix UniconOS to 2607.2 CR or later on the Current Release track, or to 2603 LTSR CU2 or later on the LTSR track, following the instructions in Citrix advisory CTX697187 (https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX697187). Because the vulnerability is local and requires low-privilege authenticated access (AV:L/PR:L), the highest-value compensating control until patching is to reduce the number of accounts that can log on locally to UniconOS devices: restrict interactive local logon to a small, audited administrative group, remove shared or generic low-privilege local accounts, and enforce per-user credentials, accepting the operational trade-off of tighter help-desk and field-service workflows. Where local access cannot be restricted, enforce least privilege so that no local account holds rights beyond its role, since a compromised low-privilege account is the documented prerequisite; this does not remove the bug but lowers the value of a foothold. Additionally, apply host-based monitoring for unexpected persistence artifacts (new startup or scheduled entries, modified service definitions, and unexpected child processes spawning from low-privileged sessions) and alert on their creation, recognizing that this is detection rather than prevention. If patching cannot be completed during a maintenance window, isolate affected devices so that local user populations are trusted and constrained, and prioritize the update for any UniconOS instance where low-privilege local access is broadly granted.

Affected VersionsENISA

UniconOS 0 <2607.2 CR
UniconOS 0 <2603 LTSR CU2

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

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

Technical ContextAI · show details

UniconOS is a Citrix-managed operating system for endpoint and appliance-style deployments, distributed on two release tracks: a rapid Current Release (CR) track and a long-term servicing LTSR track with cumulative updates (CU). The reported defect is a persistence mechanism in the OS that permits command execution to survive ordinary runtime operations, which is why Citrix classifies the issue as 'Persistent Command Execution' rather than a one-shot code-execution bug. The source data does not assign a CWE, so no authoritative root-cause class can be cited; the observed behavior (locally injected, persistence-capable command execution) maps most closely to command-injection/improper-privilege-management style weaknesses (e.g. CWE-78, CWE-269), but that mapping is an inference and not a vendor-confirmed classification. The assessed CVSS:3.1 vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L indicates the attack surface is the local device: the exploit chain begins with low-privilege authenticated access on the endpoint, requires no user interaction, and does not cross a privilege boundary beyond the vulnerable component (S:U). Impact is weighted toward confidentiality (C:H) with limited integrity and availability effects (I:L/A:L), consistent with an attacker reading or exfiltrating privileged data and retaining a persistence foothold rather than crashing or fully reconfiguring the system.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (citrix) PRIMARY 6.9 MEDIUM
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N
vuln.today AI 6.6 MEDIUM

Local vector and low-privilege authenticated access justify AV:L and PR:L with AC:L and no UI; confidentiality impact is high while integrity/availability are low, matching the vendor vector.

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

Primary rating from Vendor (citrix).

CVSS VectorVendor: citrix

Attack Vector
Local
Attack Complexity
Low
Attack Requirements
None
Privileges Required
Low
User Interaction
None
Vulnerable system: Confidentiality
High
Vulnerable system: Integrity
Low
Vulnerable system: Availability
Low
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

Lifecycle Timeline

1
Patch available
Oct 13, 2026 - 23:20 EUVD

DescriptionCVE.org

Vulnerability in Citrix UniconOS leading to Persistent Command Execution

This issue affects UniconOS: before 2607.2 CR and before 2603 LTSR CU2.

Threat Intelligence Overview

EPSS Score
0.2%
Top 91% exploitable
Prevalence
Low
niche Citrix thin-client/endpoint OS, limited enterprise footprint
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 MEDIUM
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
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
Defer
Exploitation
None
System Exposure· derived
Small
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

34
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +34
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

OS command injection occurs when an application passes unsanitized user input directly into system shell commands.

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