What is CVE-2021-37311?

CVE-2021-37311 is a high-severity vulnerability in Fcitx 5 Project, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 7.5/10. Published 2023-02-03.

How severe is CVE-2021-37311?

High severity. CVSS v3 base score is 7.5 out of 10.

Buffer overflow in Fcitx 5 Project

CVE-2021-37311

Buffer Overflow vulnerability in fcitx5 5.0.8 allows attackers to cause a denial of service via crafted message to the application's listening port.

Vulnerability class: Buffer Overflow

Published 2023-02-03 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.009 (59.0th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 59.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

Fcitx 5 Project — versions 5.0.8

Weakness classification (CWE)

CWE-120 — Buffer Copy without Checking Size of Input (Classic Buffer Overflow)

References

fcitx-im.org (Product)
github.com/fcitx/fcitx5/pull/308 (Exploit, Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-37311?: CVE-2021-37311 is a high-severity vulnerability in Fcitx 5 Project, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 7.5/10. Published 2023-02-03.
How severe is CVE-2021-37311?: High severity. CVSS v3 base score is 7.5 out of 10.