What is CVE-2021-27351?

CVE-2021-27351 is a medium-severity vulnerability in Telegram, classified under Insufficient Session Expiration. CVSS score: 5.3/10. Published 2021-02-19.

How severe is CVE-2021-27351?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Telegram

CVE-2021-27351

The 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.

Published 2021-02-19 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.008 (56.4th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 56th percentile — 56.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-613 — Insufficient Session Expiration

References

0ffsecninja.github.io/Telegram:CVE-2021-2735.html (Third Party Advisory)
security.gentoo.org/glsa/202105-07 (vendor-advisory, Third Party Advisory)

Frequently asked questions

What is CVE-2021-27351?: CVE-2021-27351 is a medium-severity vulnerability in Telegram, classified under Insufficient Session Expiration. CVSS score: 5.3/10. Published 2021-02-19.
How severe is CVE-2021-27351?: Medium severity. CVSS v3 base score is 5.3 out of 10.