CVE-2017-15721

In Irssi before 1.0.5, certain incorrectly formatted DCC CTCP messages could cause a NULL pointer dereference. This is a separate, but similar, issue relative to CVE-2017-9468.

Published: 2017-10-22 Last update: 2026-05-13 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2017-15721 is rated Moderate Risk (54.4/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.60%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2017-15721

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-28 0.71% 0.60% -0.10%
2 2026-04-15 1.14% 0.71% -0.43%
3 2025-03-30 — 1.14% —

Full EPSS history (8 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2017-15721

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.0 HIGH
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2017-15721

OS Trackers for CVE-2017-15721

vendor priority summary link
alpine — CVE-2017-15721: 1 source package rows (irssi); 11 state rows across 11 repos (3.10-main, 3.11-main, 3.12-main, 3.17-main, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community, edge-main); fixed 11, open 0. https://security.alpinelinux.org/vuln/CVE-2017-15721
debian not yet assigned CVE-2017-15721 not yet assigned priority: Debian including 1 source packages (irssi), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2017-15721
redhat medium — https://access.redhat.com/security/cve/CVE-2017-15721
ubuntu medium CVE-2017-15721 medium priority: Ubuntu including 1 source packages (irssi), 5 status rows across 5 suites (artful, trusty, upstream, xenial, zesty): released 4, needs-triage 1. https://ubuntu.com/security/CVE-2017-15721

Affected software / configurations for CVE-2017-15721

Vendor Product Version Raw CPE
irssi irssi <= 1.0.4 cpe:2.3:a:irssi:irssi:*:*:*:*:*:*:*:*
debian debian_linux 7.0 cpe:2.3:o:debian:debian_linux:7.0:*:*:*:*:*:*:*
debian debian_linux 8.0 cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

References for CVE-2017-15721

URL Tags
http://openwall.com/lists/oss-security/2017/10/22/4 Mailing List Mitigation Patch Third Party Advisory
https://irssi.org/security/irssi_sa_2017_10.txt Mitigation Patch Vendor Advisory
https://lists.debian.org/debian-lts-announce/2017/12/msg00022.html Mailing List Third Party Advisory
https://www.debian.org/security/2017/dsa-4016 Third Party Advisory
cvelogic Threat Intelligence