CVE-2021-27351
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 · uneditedThe Terminate Session feature in the Telegram application through 7.2.1 for Android, and through 2.4.7 for Windows and UNIX, fails to invalidate a recently active session.
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 Terminate Session feature in Telegram through 7.2.1 for Android and 2.4.7 for Windows/UNIX fails to properly invalidate recently active sessions. When a user attempts to terminate a session, the session remains valid and accessible rather than being fully revoked.
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<= 2.4.7<= 7.2.1CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
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 Telegram version on Windows or UNIXOpen Telegram desktop application, go to Settings > Advanced > Version, or check the application's 'About' or 'Version' information in the application menu or properties.Affected if The displayed version number is 2.4.7 or lower
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Check installed Telegram version on AndroidOpen the Telegram app on your Android device, navigate to Settings (three-line icon) > Settings, then look for the version number typically displayed at the bottom of the settings screen, or check via Google Play Store app listing.Affected if The displayed version number is 7.2.1 or lower
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Verify session termination functionalityOpen Telegram on a secondary device and log in with the same account to create multiple active sessions. Then, from one device, go to Settings > Privacy and Security > Active Sessions > Terminate Session for the other session. Wait a moment and attempt to use the terminated session (send a message or refresh) to see if it remains functional.Affected if The previously terminated session still responds to commands or shows as active after termination was requested
You are affected if your Telegram version is 2.4.7 or lower (Windows/UNIX) or 7.2.1 or lower (Android), AND you have used the session termination feature which may have left sessions still active.
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 dataAwait the official Telegram patch and verify session termination works correctly after updating; consider using alternative communication platforms until the fix is deployed.
- Consultation2.0 h
- Testing1.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-27351 — 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-2021-27351 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