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CVE-2020-8955: irc_mode_channel_update in plugins/irc/irc-mode.c in WeeChat through 2.7 allows remote attackers to cause a de

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CRITICAL 9.8REMOTEWATCHLISTUPGRADEMITIGATEDOWNGRADE

CVE-2020-8955 is a critical-severity flaw (CVSS 9.8) affecting weechat, fedora, backports sle. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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).

Why this priority

  • Critical severity
  • Remotely exploitable, no login, no user action
  • On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score9.8 (Critical)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance3.4% (top 11%)
CISA exploited listNo
WeaknessCWE-120
Published2020-02-12
Last modified2026-06-17
Publisher (CNA): MITRE · Vendor: debian · fedoraproject · opensuse · weechat

Share: LinkedIn · X · Reddit

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

weechat weechat UPGRADE
Affected: >= 0.3.8 and <= 2.7
Fixed in: newer than 2.7
Safe to downgrade to: a release before 0.3.8
1. Check installed version
apt-cache policy weechat || rpm -q weechat || weechat --version
2. UPGRADE to newer than 2.7 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade weechat
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade weechat
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 0.3.8 (Debian / Ubuntu)
apt-cache madison weechat sudo apt install weechat=<VERSION_BEFORE_0.3.8> sudo apt-mark hold weechat
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list weechat sudo dnf downgrade weechat-<VERSION_BEFORE_0.3.8> sudo dnf versionlock add weechat
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
fedoraproject fedora MITIGATE
Affected: 30 · 31 · 32
Fixed in: no fixed release known
Safe to downgrade to: a release before 30
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
opensuse backports sle DOWNGRADE
Affected: 15.0 · 15.0 sp1
Fixed in: no fixed release known
Safe to downgrade to: a release before 15.0
1. Check installed version
apt-cache policy backports-sle || rpm -q backports-sle || backports-sle --version
2. No fixed release: DOWNGRADE to a release before 15.0 (Debian / Ubuntu)
apt-cache madison backports-sle sudo apt install backports-sle=<VERSION_BEFORE_15.0> sudo apt-mark hold backports-sle
2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list backports-sle sudo dnf downgrade backports-sle-<VERSION_BEFORE_15.0> sudo dnf versionlock add backports-sle
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
opensuse leap MITIGATE
Affected: 15.1
Fixed in: no fixed release known
Safe to downgrade to: a release before 15.1
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
debian debian linux MITIGATE
Affected: 8.0 · 9.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 8.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-8955?

weechat: upgrade to newer than 2.7; fedora: mitigate or apply the listed mitigation; backports sle: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-8955 being exploited?

CVE-2020-8955 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-8955 affect?

CVE-2020-8955 affects weechat, fedora, backports sle. Severity is critical (CVSS 9.8). 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

How urgent is CVE-2020-8955?

Priority 67/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities

Related CVEs

References

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