What is CVE-2017-15721?

CVE-2017-15721 is a high-severity vulnerability in Irssi, classified under NULL Pointer Dereference. CVSS score: 7.5/10. Published 2017-10-22.

How severe is CVE-2017-15721?

High severity. CVSS v3 base score is 7.5 out of 10.

NULL pointer dereference in Irssi

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 modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.024 (83.2th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 83rd percentile — 83.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.024 · newest: 0.024 · change: 0.000

Affected products

Irssi
Debian Linux — versions 7.0, 8.0, 9.0

Weakness classification (CWE)

CWE-476 — NULL Pointer Dereference

References

www.debian.org/security/2017/dsa-4016 (vendor-advisory, Third Party Advisory)
lists.debian.org/debian-lts-announce/2017/12/msg00022.html (mailing-list, Mailing List, Third Party Advisory)
irssi.org/security/irssi_sa_2017_10.txt (Patch, Mitigation, Vendor Advisory)
openwall.com/lists/oss-security/2017/10/22/4 (Patch, Mailing List, Third Party Advisory, Mitigation)

Frequently asked questions

What is CVE-2017-15721?: CVE-2017-15721 is a high-severity vulnerability in Irssi, classified under NULL Pointer Dereference. CVSS score: 7.5/10. Published 2017-10-22.
How severe is CVE-2017-15721?: High severity. CVSS v3 base score is 7.5 out of 10.