CVE-2026-21133

Executive Summary

CVE-2026-21133 is a path traversal vulnerability in Samsung Flow prior to version 4.9.22.1 that permits local attackers to access clipboard data. The flaw resides in an application designed to bridge mobile and desktop workflows, meaning affected systems are those where Samsung Flow is installed and running with local access. Since no public exploit or patch evidence is currently tracked, exploitation requires local access to the target device, but successful abuse can result in unauthorized disclosure of sensitive clipboard contents, which often include passwords, tokens, or personal data.

Technical Analysis

The vulnerability is classified as a path traversal (CWE-22) issue affecting Samsung Flow versions prior to 4.9.22.1. Path traversal vulnerabilities occur when an application constructs filesystem paths using externally influenced input without properly neutralizing directory traversal sequences such as "../" or absolute paths. In this instance, the vulnerable component allows a local attacker to traverse outside an intended directory boundary and access clipboard data. The NVD description explicitly states that the impact is unauthorized access to clipboard data, which suggests the flaw enables reading clipboard contents that would otherwise be isolated from the attacker's context. The mechanism by which the clipboard data is stored or referenced via a filesystem path is not detailed in the available intelligence. Consequently, the exact function names, file paths, or API parameters involved cannot be confirmed from the provided data. The attack surface is local: the attacker must already have some level of access to the device where Samsung Flow is installed, consistent with the "local attackers" phrasing in the NVD description. No CVSS score, vector, or CWE mapping was provided directly in the source data, though the vulnerability class aligns with CWE-22. The absence of a public PoC, Nuclei template, or exploit code means the technical mechanics remain inferred from the vulnerability class rather than observed in the wild.

Exploitation Scenarios

No public PoC is available; the attack chain is inferred from the vulnerability class and the sparse description provided. The following scenario is strictly limited to what can be derived from the NVD description and general path traversal mechanics.

1. Reconnaissance/target identification: The attacker gains local access to a system where Samsung Flow (prior to 4.9.22.1) is installed. This could be a shared workstation, a compromised endpoint, or a device where the attacker has user-level privileges. The attacker identifies that Samsung Flow is present and running, potentially by enumerating installed applications or running processes.

2. Triggering the flaw: The attacker interacts with the Samsung Flow application in a manner that causes it to process a crafted path input. Because the vulnerability is a path traversal, the attacker supplies input containing directory traversal sequences or an absolute path that causes the application to resolve a file location outside the intended clipboard storage or access boundary. The exact input vector (e.g., a file picker, a configuration setting, an inter-process communication message) is not specified in the available data and cannot be fabricated.

3. Payload/execution method: At the vulnerability-class level, the attacker uses the path traversal to redirect the application's file access to a location containing clipboard data. The payload is the crafted path string itself; no code execution is required. The goal is to cause the application to read clipboard-related content that the attacker should not be able to access.

4. Post-exploitation impact: Successful exploitation results in the local attacker obtaining clipboard data. Clipboard contents frequently include sensitive information such as passwords, authentication tokens, financial data, or personal communications. The attacker can use this information for lateral movement, credential theft, or further compromise of the user's accounts and systems. The impact is limited to confidentiality (unauthorized read access), with no evidence of integrity or availability impact from the description.

Impact Assessment

The business impact of CVE-2026-21133 centers on confidentiality loss. Clipboard data on enterprise endpoints often contains credentials, multi-factor authentication codes, API keys, or sensitive business text. A local attacker who can read this data may escalate privileges, bypass authentication, or exfiltrate proprietary information. The blast radius is limited to systems where Samsung Flow prior to 4.9.22.1 is installed and where an attacker has local access. Because the vulnerability requires local access and user interaction is not indicated as necessary (the NVD description does not mention user interaction), the attack complexity is low for an attacker who already has a foothold. No CVSS score or subscores were provided in the source data; therefore, no quantitative severity can be asserted. The absence of CISA KEV listing and the lack of public exploit code suggest that exploitation is not currently widespread, but the vulnerability remains a credible insider threat or post-compromise escalation vector.

Detection Guidance

Sigma Rule

title: Samsung Flow Path Traversal Clipboard Access Attempt
id: 8f4c2a1e-3b7d-4e9f-a1c2-6d8e5f7a9b0c
status: experimental
description: Detects potential path traversal exploitation in Samsung Flow prior to 4.9.22.1 targeting clipboard data
author: valtersit.com
date: 2026-01-01
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\Samsung Flow.exe'
            - '\SamsungFlow.exe'
    filter:
        CommandLine|contains:
            - '..\'
            - '../'
            - '%2e%2e%2f'
            - '%2e%2e/'
            - '..%5c'
            - '%2e%2e%5c'
    condition: selection and filter
falsepositives:
    - Legitimate application paths containing traversal sequences (rare)
level: medium
tags:
    - attack.t1083
    - cve.2026.21133

YARA Rule

rule CVE_2026_21133_Samsung_Flow_Path_Traversal
{
    meta:
        description = "Detects path traversal strings targeting Samsung Flow clipboard access"
        author = "valtersit.com"
        date = "2026-01-01"
        reference = "CVE-2026-21133"
        severity = "medium"

    strings:
        $s1 = "Samsung Flow" ascii wide nocase
        $s2 = "clipboard" ascii wide nocase
        $t1 = "..\\" ascii wide
        $t2 = "../" ascii wide
        $t3 = "%2e%2e%2f" ascii wide nocase
        $t4 = "..%5c" ascii wide nocase

    condition:
        $s1 and $s2 and any of ($t*)
}

Suricata IDS Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-21133 Samsung Flow Path Traversal Clipboard Access Attempt"; flow:to_server,established; content:"Samsung Flow"; http_header; nocase; content:"..%2f"; http_uri; nocase; content:"..%5c"; http_uri; nocase; classtype:attempted-user; reference:cve,2026-21133; sid:202621133; rev:1;)

Elastic Detection

process where process.name : ("Samsung Flow.exe", "SamsungFlow.exe") and
  process.command_line : ("*..\\*", "*../*", "*%2e%2e%2f*", "*..%5c*")

Splunk SPL Query

index=windows EventCode=4688 (Image="*Samsung Flow.exe" OR Image="*SamsungFlow.exe")
| search CommandLine="*..\\*" OR CommandLine="*../*" OR CommandLine="*%2e%2e%2f*" OR CommandLine="*..%5c*"
| table _time, ComputerName, User, Image, CommandLine, ParentImage
| sort - _time

Wazuh OSSEC Rule

<group name="windows,samsung_flow,">
  <rule id="100133" level="10">
    <if_sid>61603</if_sid>
    <field name="win.eventdata.image">Samsung Flow.exe|SamsungFlow.exe</field>
    <field name="win.eventdata.commandLine">\.\.\\|\.\./|%2e%2e%2f|\.\.%5c</field>
    <description>CVE-2026-21133: Possible Samsung Flow path traversal attempt targeting clipboard data</description>
    <mitre>
      <id>T1083</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate mitigations:

   • Restrict local access to systems running Samsung Flow. Ensure only trusted users have interactive logon rights.
   • Monitor for anomalous process behavior involving Samsung Flow, particularly command lines or parameters containing path traversal sequences.
   • Consider disabling or uninstalling Samsung Flow on endpoints where it is not operationally required, especially in high-security environments.
   • Implement application allowlisting to prevent unauthorized interaction with the Samsung Flow process.
   • Clear clipboard contents automatically after a short timeout using endpoint management policies to reduce the window of exposure.

2. Patch/upgrade steps:

   • No patch is currently available from tracked sources. The NVD description indicates that versions prior to 4.9.22.1 are affected. Monitor Samsung's official channels and the NVD entry for CVE-2026-21133 for a fixed release. Once version 4.9.22.1 or later is available, upgrade immediately.
   • Verify the installed version of Samsung Flow through the application's about screen or installed programs list before and after upgrading.

3. Long-term hardening:

   • Enforce the principle of least privilege to limit the number of users who can interact with the application locally.
   • Deploy endpoint detection and response (EDR) solutions with behavioral monitoring for path traversal patterns and clipboard access anomalies.
   • Conduct regular security reviews of desktop integration tools that bridge mobile and desktop environments, as they often introduce cross-boundary data flows.
   • Implement data loss prevention (DLP) controls to detect and block unauthorized clipboard exfiltration.

References

1. NVD Entry for CVE-2026-21133: https://nvd.nist.gov/vuln/detail/CVE-2026-21133
2. Samsung Flow Official Website: https://www.samsung.com/global/galaxy/apps/samsung-flow/
3. CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'): https://cwe.mitre.org/data/definitions/22.html
4. MITRE ATT&CK T1083: File and Directory Discovery: https://attack.mitre.org/techniques/T1083/
5. CISA Known Exploited Vulnerabilities Catalog (not listed as of report date): https://www.cisa.gov/known-exploited-vulnerabilities-catalog