Security readout for executives and security teams
Plain-English summary
A critical Synology Chat Server flaw can let a remote, authenticated attacker abuse a user interface interaction to access or alter arbitrary DSM files or disrupt service. Systems running versions earlier than 2.4.5-22148 should be treated as urgent remediation targets.
Executive priority
Prioritize remediation immediately for affected production systems because exploitation could compromise DSM file confidentiality and integrity or interrupt service. Require owners to confirm versions and update completion. Escalate any evidence of unexplained file changes or outages for incident investigation.
Technical view
CVE-2026-40541 is a CWE-79 cross-site scripting vulnerability in Synology Chat Server's extract domain. It affects releases before 2.4.5-22148. The CVSS 3.1 score is 9.0, reflecting network reachability, low complexity, required low privileges and user interaction, changed scope, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure exists where an affected Synology Chat Server is reachable by authenticated users. Exploitation requires low privileges and user interaction. The supplied sources do not establish whether internet exposure is necessary or identify specific vulnerable configurations beyond the affected version range.
Exploitation context
The supplied bundle does not identify this CVE as CISA KEV-listed and provides no evidence of active exploitation or a public exploit. Nevertheless, successful exploitation could read or modify arbitrary DSM files and cause denial of service.
Researcher notes
The source description names improper output neutralization in the extract domain but does not provide the vulnerable input path, affected workflow, indicators, or technical patch details. Avoid assuming stored versus reflected XSS or a specific attack chain. Validation should focus on authoritative version checks and defensive review without attempting exploitation.
Mitigation direction
- Upgrade Synology Chat Server to version 2.4.5-22148 or later.
- Confirm the applicable update and installation guidance in Synology's security advisory.
- Restrict Chat Server access to trusted users and networks until remediation is complete.
- Investigate potentially affected systems if unauthorized file changes or service disruption occurred.
Validation and detection
- Inventory every Synology Chat Server instance and record its installed version.
- Verify no instance remains on a release earlier than 2.4.5-22148.
- Confirm the updated package is running successfully after installation.
- Review available DSM and Chat Server logs for suspicious authenticated activity.
- Check critical DSM files for unexpected access or modification where evidence is available.
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-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. 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-2026-40541 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
- Critical
- CVSS
- 9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/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:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H2.36synologyVulnerability scoring details
Base CVSS 3.1 score
9CriticalVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/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-26:10 Synology Chat ServerCVE 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.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.