CVE-2024-39844Network attack vector

Remote code execution via unescaped KICK reason

Published Jul 3, 2024 · Updated Aug 2, 2024

Code injection in ZNC before 1.9.1 allows remote attackers to execute arbitrary code through a crafted IRC KICK reason. The modtcl OnKick handler inserts the unescaped reason and channel name into a Tcl command string passed to Tcl_Eval, allowing Tcl metacharacters to alter the command. Exploitation requires modtcl to be loaded by a ZNC administrator and IRC channel privileges sufficient to issue KICK, and grants execution in the ZNC process context.

CVSS severity9.8
Critical
EPSS probability3.86%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Code injection in ZNC before 1.9.1 allows remote attackers to execute arbitrary code through a crafted IRC KICK reason. The modtcl OnKick handler inserts the unescaped reason and channel name into a Tcl command string passed to Tcl_Eval, allowing Tcl metacharacters to alter the command. Exploitation requires modtcl to be loaded by a ZNC administrator and IRC channel privileges sufficient to issue KICK, and grants execution in the ZNC process context.

The record

CVE
CVE-2024-39844
Published
Jul 3, 2024
Updated
Aug 2, 2024
Vendor
ZNC
Product
ZNC
Classifications
CWE-94, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 3, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <1.9.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ZNC · ZNCversion=0 <1.9.1

Published CVSS scores

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo