dbcve.org
Debian LinuxOperating system · Debian

CVE-2021-29376

HIGH · 7.5 CVSS v3.1 Published 2021-03-30
Fix available
A fix is available. Upgrade to 20210314 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
ircII before 20210314 allows remote attackers to cause a denial of service (segmentation fault and client crash, disconnecting the victim from an IRC server) via a crafted CTCP UTC message.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

ircII IRC client versions before 20210314 contain a vulnerability in CTCP UTC message parsing. Attackers can send a crafted CTCP UTC message that triggers a segmentation fault, causing the client to crash and disconnect the victim from the IRC server.

MitigationUpdate ircII to version 20210314 or later to obtain the patch that properly handles CTCP UTC message input validation.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Debian LinuxOperating system
Affected:= 9.0
IrciiApplication
Affected:< 20210314

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check if ircII is installed
    Run command: dpkg -l | grep -i ircii or which irc or which epython
    Affected if ircII is not installed on the system
  2. Identify installed ircII version
    Run command: irc --version or ircii --version, or check package manager: dpkg -l ircii
    Affected if Version is present but shows a date earlier than 20210314 (e.g., 20210101, 20201231, etc.) or package version is earlier than 20210314
  3. Verify CTCP UTC message handling is active
    Check if the client has been configured to accept or parse CTCP messages - review ~/.ircrc or ~/.irssi/config for CTCP-related settings, or simply test by receiving a CTCP UTC query from another user
    Affected if The client can receive and process CTCP messages without being explicitly disabled in configuration
  4. Confirm client crash behavior with CTCP UTC
    If possible, have a test partner send a CTCP UTC command (\x01UTC\x01) to the running ircII client
    Affected if Client crashes, disconnects, or segfaults upon receiving the CTCP UTC message

User is affected if ircII version is installed and is earlier than 20210314, and the client is configured to accept CTCP messages which can trigger a crash when receiving a crafted UTC message.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to 20210314 or later
Fixed in 20210314
Interim mitigation

Update ircII to version 20210314 or later to obtain the patch that properly handles CTCP UTC message input validation.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,190
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,904.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-29376 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-29376 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data