Unrated

Unauthenticated arbitrary file read/write and DoS in Synology MailPlus Server

IdentifiersCVE-2026-13136CWE-863

CVE-2026-13136 is a critical authorization flaw in Synology MailPlus Server on DiskStation Manager (DSM). The vulnerability is associated with CWE-863 (Incorrect Authorization) and allows a remote attacker to access functionality without authentication over the network. Successful exploitation can enable arbitrary file read and arbitrary file write operations and can also be used to trigger denial-of-service conditions. The issue affects MailPlus Server deployments on DSM 7.3, 7.2.2, and 7.2.1 prior to the fixed releases identified by Synology.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can result in unauthorized disclosure and modification of data through arbitrary file read and write capabilities, with corresponding loss of confidentiality and integrity. The vulnerability can also be leveraged to disrupt service availability by causing denial of service. Given the reported lack of authentication requirement and network reachability, exposed systems are at risk of full compromise of affected application data and operational interruption.

Mitigation

If you can’t patch tonight, do this now.

No vendor workaround or mitigation is available beyond applying the security updates. Where immediate patching is not possible, reducing external exposure of MailPlus Server and limiting network access may reduce attack surface, but this does not constitute a vendor-provided fix.

Remediation

Patch, then assume compromise.

Upgrade Synology MailPlus Server to a fixed version. For DSM 7.3, upgrade to MailPlus Server 4.0.1-31663 or later. For DSM 7.2.2 and DSM 7.2.1, upgrade to MailPlus Server 4.0.1-21663 or later. Synology states that the vulnerabilities are resolved in these updated releases.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

SynologyMailplus Serverapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

9 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

9 SOURCESView more in app

cyber security newsNews

Jun 30, 2026

Synology MailPlus Server Vulnerabilities Allow Attackers to Trigger DoS Attacks

A critical unauthenticated network-exploitable vulnerability in Synology MailPlus Server that can allow arbitrary file read/write and denial-of-service, with maximum CVSS 10.0 severity.

synologyNews

Jun 26, 2026

Synology_SA_26_11 | Synology Inc.

A critical Synology MailPlus Server vulnerability that allows remote attackers to read or write arbitrary files and cause denial-of-service.

What this page doesn’t show

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity6