VulnerabilityPublished 28 Jan 2026

CVE-2025-59899: Flexense Sync Breeze Enterprise Server · XSS or 'Cross-site Scripting'

Affects Flexense Sync Breeze Enterprise ServerSource CVE Database V5

Not known to be exploited · CVSS 5.1 Medium.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 4.0 base score

5.1Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: Passive
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: Low
Subsequent system integrity: Low
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Subsequent System.
Subsequent system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
FlexenseSync Breeze Enterprise Server	Affected =10.4.18	Fixed in–
FlexenseDisk Pulse Enterprise	Affected =10.4.18	Fixed in–

AI-suggested

Apply patches or updates from Flexense as soon as they become available to address the input validation flaws.
Until patches are released, restrict access to the Sync Breeze Enterprise Server web interface to trusted users and networks only, using network segmentation and firewall rules.
Implement Web Application Firewall (WAF) rules to detect and block suspicious input patterns targeting the vulnerable parameters.
Conduct input validation and sanitization on the server side for all user-supplied data, especially in the affected parameters, to neutralize malicious scripts.
Educate authenticated users about the risks of clicking on suspicious links or content within the application to reduce the chance of exploitation.
Monitor logs and user activity for unusual behavior indicative of XSS exploitation or session hijacking attempts.
Consider disabling or limiting the use of affected parameters if they are not essential to operations.
Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts within the web application context.
Regularly review and audit web application security controls and user privileges to minimize exposure.

Description

Sync Breeze Enterprise Server v10.4.18 and Disk Pulse Enterprise v10.4.18 contain a persistent authenticated Cross-Site Scripting (XSS) vulnerability. An attacker could send malicious content to an authenticated user and steal information from their session due to insufficient validation of user input in '/server_options?sid=', affecting the 'tasks_logs_dir', 'errors_logs_dir', 'error_notifications_address', 'status_notifications_address', and 'status_reports_address' parameters.

Impact

For European organizations, this vulnerability poses a risk of session hijacking and unauthorized access to sensitive information through the exploitation of persistent XSS. Organizations using Sync Breeze Enterprise Server for file synchronization and monitoring could see compromised user sessions, leading to potential data leakage or unauthorized actions performed under the guise of legitimate users. While the vulnerability does not directly impact system availability or integrity, the confidentiality breach can have downstream effects such as unauthorized data access or lateral movement within networks. Sectors such as finance, healthcare, and critical infrastructure that rely on secure file management and monitoring are particularly at risk. The requirement for authentication limits the attack surface to internal or trusted users, but social engineering or credential compromise could enable attackers to exploit this vulnerability. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers often develop exploits post-disclosure. European organizations must consider the regulatory implications of data breaches resulting from such vulnerabilities, including GDPR compliance and potential fines.

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

incibe.es/en/incibe-cert/notices/aviso/multiple-vulnerabilities-flexense-products (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Jan 2026, 12:22 UTC

WeaknessesCWE-79

Technical details

References

Community reviews

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