VulnerabilityPublished 8 Mar 2026Updated 11 Mar 2026

CVE-2026-3749: Bytedesk · Unrestricted Upload

Affects BytedeskSource CVE Database V5

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Public exploit available · CVSS 5.3 Medium.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score

5.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 38% 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:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P

Base metrics

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

Threat metrics

Exploit Maturity: POC

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: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable 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 Vulnerable System.
Vulnerable 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 Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable 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.
Exploit Maturity: POC: Based on threat intelligence sources each of the following must apply: · Proof-of-concept is publicly available · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 8 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CVSS exploit maturity: proof of concept public
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), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 30 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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
Bytedesk	Affected 1.3.0 – 1.3.9 10 affected builds	Fixed in–
GitHubbytedesk/bytedesk`pkg:github/bytedesk/bytedesk`Other threats	Affected 1.3.0 – 1.3.9 10 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate CVE-2026-3749, organizations should immediately upgrade Bytedesk to version 1.4.5.1 or later, which contains the official patch addressing the unrestricted file upload vulnerability. In addition to patching, implement strict file upload controls such as validating file types, enforcing file size limits, and scanning uploaded files for malware. Employ network segmentation to limit the exposure of Bytedesk servers and restrict access to trusted users and IP addresses. Monitor logs and file upload activity for unusual or unauthorized uploads. Use web application firewalls (WAFs) with rules designed to detect and block malicious upload attempts targeting Bytedesk endpoints. Regularly audit and update security configurations to ensure no residual vulnerabilities remain. Finally, educate administrators and users about the risks associated with file uploads and the importance of applying security updates promptly.

Description

A weakness has been identified in Bytedesk up to 1.3.9. This vulnerability affects the function handleFileUpload of the file source-code/src/main/java/com/bytedesk/core/upload/UploadRestService.java of the component SVG File Handler. Executing a manipulation can lead to unrestricted upload. The attack can be executed remotely. The exploit has been made available to the public and could be used for attacks. Upgrading to version 1.4.5.1 is able to resolve this issue. This patch is called 975e39e4dd527596987559f56c5f9f973f64eff7. It is recommended to upgrade the affected component.

Impact

The unrestricted file upload vulnerability in Bytedesk can have significant consequences for organizations worldwide. Attackers exploiting this flaw can upload malicious files that may lead to remote code execution, enabling full system compromise. This can result in data theft, unauthorized access to sensitive communications, disruption of services, and potential lateral movement within networks. The vulnerability's ease of exploitation without user interaction or high privileges increases the risk of automated or mass exploitation campaigns. Organizations relying on Bytedesk for internal or external communications may face operational disruptions and reputational damage if exploited. Additionally, compromised systems could be leveraged as entry points for broader attacks against connected infrastructure. Although the CVSS score is medium, the potential for escalation and impact on confidentiality, integrity, and availability makes this a serious concern. Timely patching is critical to prevent exploitation, especially given the public availability of exploit code.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 16 Mar 2026, 09:09 UTC

Technical details

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