Security readout for executives and security teams
Plain-English summary
Synology Presto Client installers before 2.1.3-0672 can be tricked into using an attacker-placed DLL from the installer’s directory. This requires local access and someone to run the installer, but successful abuse could affect file confidentiality, integrity, and availability during installation.
Executive priority
Treat this as a moderate endpoint hygiene and software deployment risk. Prioritize remediation where Presto Client is installed through shared folders, manual downloads, or user-writable staging paths.
Technical view
CVE-2026-3091 is a CWE-427 uncontrolled search path element issue in Synology Presto Client before 2.1.3-0672. A local user can pre-position a malicious DLL in the same directory as the installer, leading to arbitrary file read/write or denial-of-service during installation.
Likely exposure
Exposure is mainly on workstations or servers where Synology Presto Client is installed or upgraded from a directory writable by lower-privileged local users.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation evidence. The CVSS vector requires local access, low privileges, high attack complexity, and user interaction.
Researcher notes
This appears to be an installer search-path weakness, not a remotely reachable service flaw. Evidence is limited to the CVE and vendor advisory details provided; avoid assuming broader affected Synology products or confirmed exploitation.
Mitigation direction
- Upgrade Synology Presto Client to version 2.1.3-0672 or later.
- Check Synology’s advisory for any updated remediation guidance.
- Run installers from trusted, access-controlled directories only.
- Restrict write access to software staging and download locations.
- Remove stale installer files from shared or user-writable folders.
Validation and detection
- Inventory systems with Synology Presto Client installed.
- Verify installed versions are 2.1.3-0672 or later.
- Review deployment tooling for installer source paths and folder permissions.
- Check whether local users can write beside the installer.
- Confirm software distribution shares are not broadly writable.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-427: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-3091 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H0.85.9synologyVulnerability scoring details
Base CVSS 3.1 score
6.7MediumVector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- Synology-SA-26:02 Synology Presto ClientCVE reference, synology · vendor-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Uncontrolled Search Path Element
Uncontrolled Search Path Element represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.