Actual Sync Server up to 26.2.1 /sync/upload-user-file path traversal

CVSS Meta Temp Score
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CTI Interest Score
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5.2$0-$5k0.00

Summaryinfo

A vulnerability classified as critical has been found in Actual Sync Server up to 26.2.1. This impacts an unknown function of the file /sync/upload-user-file. This manipulation causes path traversal. This vulnerability is handled as CVE-2026-3089. The attack can be initiated remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Actual Sync Server up to 26.2.1. Affected by this vulnerability is some unknown processing of the file /sync/upload-user-file. The manipulation with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect integrity, and availability. The summary by CVE is:

Actual Sync Server allows authenticated users to upload files through POST /sync/upload-user-file. In versions prior to 26.3.0, improper validation of the user-controlled x-actual-file-id header means that traversal segments (../) can escape the intended directory and write files outside userFiles.This issue affects prior versions of Actual Sync Server 26.3.0.

The weakness was released by Juan Patarroyo. It is possible to read the advisory at fluidattacks.com. This vulnerability is known as CVE-2026-3089 since 02/24/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1006 according to MITRE ATT&CK.

Upgrading to version 26.3.0 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-10340). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 5.4
VulDB Meta Temp Score: 5.2

VulDB Base Score: 5.4
VulDB Temp Score: 5.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Path traversal
CWE: CWE-22
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Sync Server 26.3.0
Patch: github.com

Timelineinfo

02/24/2026 CVE reserved
03/09/2026 +13 days Advisory disclosed
03/09/2026 +0 days VulDB entry created
03/12/2026 +3 days VulDB entry last update

Sourcesinfo

Advisory: fluidattacks.com
Researcher: Juan Patarroyo
Status: Confirmed

CVE: CVE-2026-3089 (🔒)
GCVE (CVE): GCVE-0-2026-3089
GCVE (VulDB): GCVE-100-349831
EUVD: 🔒

Entryinfo

Created: 03/09/2026 15:59
Updated: 03/12/2026 21:44
Changes: 03/09/2026 15:59 (69), 03/09/2026 17:33 (2), 03/12/2026 21:44 (1)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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