What is CVE-2020-8955?

CVE-2020-8955 is a critical-severity vulnerability in Weechat, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 9.8/10. Published 2020-02-12.

How severe is CVE-2020-8955?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Weechat

CVE-2020-8955

irc_mode_channel_update in plugins/irc/irc-mode.c in WeeChat through 2.7 allows remote attackers to cause a denial of service (buffer overflow and application crash) or possibly have unspecified other impact via a malformed IRC message 324 (channel mode).

Vulnerability class: Buffer Overflow

Published 2020-02-12 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.034 (89.0th percentile), scored 2026-11-01.

Low probability of exploitation in the next 30 days, but still tracked. 89th percentile — 89.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.037 · newest: 0.034 · change: -0.002

Affected products

Weechat
Debian Linux — versions 8.0, 9.0
Fedoraproject Fedora — versions 30, 31, 32
openSUSE Backports Sle — versions 15.0
openSUSE Leap — versions 15.1

Weakness classification (CWE)

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

References

weechat.org/doc/security/ (Vendor Advisory)
github.com/weechat/weechat/commit/6f4f147d8e86adf9ad34a8ffd7e7f1f23a7e74da (Patch, Third Party Advisory)
lists.opensuse.org/opensuse-security-announce/2020-02/msg00032.html (vendor-advisory, Mailing List, Third Party Advisory)
lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
lists.debian.org/debian-lts-announce/2020/03/msg00031.html (mailing-list, Mailing List, Third Party Advisory)
security.gentoo.org/glsa/202003-51 (vendor-advisory, Third Party Advisory)
lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
lists.debian.org/debian-lts-announce/2021/09/msg00018.html (mailing-list, Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2020-8955?: CVE-2020-8955 is a critical-severity vulnerability in Weechat, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 9.8/10. Published 2020-02-12.
How severe is CVE-2020-8955?: Critical severity. CVSS v3 base score is 9.8 out of 10.