CVE-2021-27351Network attack vector

Persistent account access via incomplete session termination

Published Feb 19, 2021 · Updated Aug 3, 2024

Insufficient session expiration in Telegram through 7.2.1 on Android and through 2.4.7 on Windows and UNIX allows remote attackers to retain access. The Terminate Session feature does not invalidate a recently active session, leaving its existing authorization usable after termination. Exploitation requires control of that session before termination; public sources disclose no lower-level implementation details or additional impact.

CVSS severity5.3
Medium
EPSS probability0.84%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient session expiration in Telegram through 7.2.1 on Android and through 2.4.7 on Windows and UNIX allows remote attackers to retain access. The Terminate Session feature does not invalidate a recently active session, leaving its existing authorization usable after termination. Exploitation requires control of that session before termination; public sources disclose no lower-level implementation details or additional impact.

The record

CVE
CVE-2021-27351
Published
Feb 19, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-613
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-613Insufficient Session Expiration

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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