CVE-2019-18224 — idn2_to_ascii_4i in lib/lookup

idn2_to_ascii_4i in lib/lookup.c in GNU libidn2 before 2.1.1 has a heap-based buffer overflow via a long domain string.

01What is this vulnerability?

idn2_to_ascii_4i in lib/lookup.c in GNU libidn2 before 2.1.1 has a heap-based buffer overflow via a long domain string.

02Affected products

No structured affected-product list available — see references below for vendor advisories.

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2019-10-21T17:15:09.930
• Last modified: 2026-10-14T07:16:49.913

09References

• lists.opensuse.org — http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00008.html
• lists.opensuse.org — http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00009.html
• bugs.chromium.org — https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=12420
• github.com — https://github.com/libidn/libidn2/commit/e4d1558aa2c1c04a05066ee8600f37603890ba8…
• github.com — https://github.com/libidn/libidn2/compare/libidn2-2.1.0...libidn2-2.1.1
• lists.fedoraproject.org — https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro…
• lists.fedoraproject.org — https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro…
• seclists.org — https://seclists.org/bugtraq/2020/Feb/4
• security.gentoo.org — https://security.gentoo.org/glsa/202003-63
• usn.ubuntu.com — https://usn.ubuntu.com/4168-1/