CVE-2021-26569
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedRace Condition within a Thread vulnerability in iscsi_snapshot_comm_core in Synology DiskStation Manager (DSM) before 6.2.3-25426-3 allows remote attackers to execute arbitrary code via crafted web requests.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceA race condition vulnerability exists in the iscsi_snapshot_comm_core component of Synology DiskStation Manager. The flaw allows remote attackers to execute arbitrary code by sending specially crafted web requests that exploit the race condition within thread handling during iSCSI snapshot operations.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 6.2.3-25426-3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Check DSM versionLog into DSM and go to Control Panel > System > System Information, or run 'grep -i product_version /etc/VERSION' via SSH to see the installed DSM versionAffected if The installed version is lower than 6.2.3-25426-3 (for example, 6.2.3-25426-2 or earlier)
-
Verify iSCSI service is enabledIn DSM, go to Storage Manager > iSCSI > iSCSI LUN or iSCSI Target to check if the iSCSI service is turned on. Alternatively, check if the iscsi_snapshot_comm_core process is running via command lineAffected if iSCSI service is actively enabled and running on the DSM system
-
Check for active iSCSI snapshotsIn DSM Storage Manager, navigate to iSCSI LUN or iSCSI Target sections and review whether any snapshot operations or snapshot schedules are configuredAffected if iSCSI snapshots are configured or actively being used on the system
-
Inspect network exposure of management interfacesReview firewall settings or network configuration to determine if DSM management interfaces (web UI ports 5000/5001) are exposed to untrusted networksAffected if DSM management interfaces are accessible from the internet or untrusted networks without proper access controls
The environment is affected if DSM version is below 6.2.3-25426-3 AND the iSCSI service is enabled, since the race condition vulnerability in the iscsi_snapshot_comm_core component can be exploited through specially crafted web requests during iSCSI snapshot operations.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data6.2.3-25426-3
Upgrade DSM to version 6.2.3-25426-3 or later. If immediate patching is not possible, consider restricting network access to DSM management interfaces and monitoring for suspicious iSCSI-related web requests.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26569 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-26569 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data