CVE-2021-27771
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 · uneditedUser SID can be modified resulting in an Arbitrary File Upload or deletion of directories causing a Denial of Service. When interacting in a normal matter with the Sametime chat application, users hold a cookie containing their session ID (SID). This value is also used when sending chat messages, receiving notifications and/or transferring files.
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 confidenceThe Sametime chat application has a vulnerability where user session IDs (SID) stored in cookies can be modified, allowing attackers to upload arbitrary files or delete directories. The SID is used for chat messages, notifications, and file transfers, but lacks proper validation, enabling unauthorized actions.
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= 11.6CVSS 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
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/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.
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Check installed Sametime versionLocate the Sametime installation directory and check the version manifest, about dialog, or version file. Common locations include the installation root or a version.info file within the program directory.Affected if The installed version is exactly 11.6 (version equals 11.6, not just containing 11.6)
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Verify web services are exposedCheck if the Sametime web interface (typically ports 8080, 8443, or 80/443 for the web client) is accessible from the network. Inspect server configuration files for enabled web connectors.Affected if The Sametime web services are running and externally accessible, as the vulnerability is exploited via HTTP requests
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Confirm file transfer feature is enabledExamine the Sametime server configuration (usually in stconfig.nsf or XML configuration files) for the file transfer/enableFileTransfer setting.Affected if File transfer capability is enabled on the server, as this is one of the attack vectors (arbitrary file upload)
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Review session cookie handlingInspect HTTP traffic or server logs for requests containing the 'SID' or session ID cookie parameter. Check if the server validates the SID against the authenticated user before processing requests.Affected if The server accepts and processes requests with SID cookies without validating them against the authenticated user session
A user is affected if they are running Sametime version 11.6 with web services and file transfer features enabled, as the vulnerability allows session ID manipulation for unauthorized file 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 dataImplement strict server-side validation of the session ID against the authenticated user and enforce proper authorization checks before allowing file operations or directory deletions.
- Consultation6.0 h
- Implementation12.0 h
- Testing10.0 h
- Review / QA5.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-27771 — 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-2021-27771 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
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- 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