Skip to content
Fencer Intel
high 7.5

CVE-2016-6263 json

The stringprep_utf8_nfkc_normalize function in lib/nfkc.c in libidn before 1.33 allows context-dependent attackers to cause a denial of ser…

published 2016-09-07 10 y ago modified 2026-06-17 4 mo ago also EUVD-2016-7193

cvss
7.5
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
4.4%
EPSS 4.4% chance of exploitation in 30 days, percentile 91%
public exploits
0
none known

Summary

The stringprep_utf8_nfkc_normalize function in lib/nfkc.c in libidn before 1.33 allows context-dependent attackers to cause a denial of service (out-of-bounds read and crash) via crafted UTF-8 data.

Patch / fix

  • libidn Debian 14, Debian 13, Debian 12 1.33-1

debian advisories DEBIAN-CVE-2016-6263

  • libidn Ubuntu 14.04 LTS 1.28-1ubuntu2.1
  • libidn Ubuntu 16.04 LTS 1.32-3ubuntu1.1

ubuntu advisories UBUNTU-CVE-2016-6263

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libidn SLES for SAP 11 SP4, SLES 11 SP4, SLE Software Development Kit 11 SP4 1.10-6.1
  • libidn SLES for SAP 12 SP1, SLES 12 SP1, SLED 12 SP1 +1 more 1.28-4.1

suse advisories SUSE-SU-2016:2291-1SUSE-SU-2016:2079-1

  • libidn Alpine 3.24, Alpine 3.23, Alpine 3.22 +20 more 1.33-r0

alpine advisories ALPINE-CVE-2016-6263

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2016-6263 updated cvss 3.7

libidn: Crash when given invalid UTF-8 data on input

  • Red Hat Enterprise Linux 5 libidn Red Hat Enterprise Linux 6 libidn Red Hat Enterprise Linux 7 libidn, emacs-libidn
    affected: no fix planned “Will not fix”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

4.37% chance of exploitation in the next 30 days, higher than 91% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.0 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.