CVE-2019-18224 — idn2_to_ascii_4i in lib/lookup.c in GNU libidn2 before 2.1.1 has a heap-based buffer overflow via...
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 3.7% (30-day exploitation probability)+13
- Technical severity (critical)+10
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — github.com (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Gnu Libidn2).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 9.8 | CVSS 3.1 | Critical | 3.9 | 5.9 | nvd@nist.gov via NIST National Vulnerability Database |
| 9.8 | CVSS 3.1 | Critical | — | — | GitHub, Inc. via GitHub Security Advisories |
| 7.5 | CVSS 2.0 | High | 10.0 | 6.4 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 3.71%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
Timeline
What happened to this CVE, newest first.
- 2026
- Record published
- Fix documented
- Affected products added · gnu/libidn2
- CVSS changed · 9.8
- Source status changed · → Modified
- Record created in this database
- 2019
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 14, 2026 – Oct 14, 2026
- 1× Official description updated · Oct 14, 2026 – Oct 14, 2026
References
17 on the record
- github.com/libidn/libidn2/commit/e4d1558aa2c1c04a05066ee8600f37603890ba8c
- nvd.nist.gov/vuln/detail/CVE-2019-18224
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JDQV
- www.debian.org/security/2020/dsa-4613
- bugs.chromium.org/p/oss-fuzz/issues/detail
- lists.opensuse.org/opensuse-security-announce/2019-12/msg00008.html
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JDQV
- lists.opensuse.org/opensuse-security-announce/2019-12/msg00009.html
- usn.ubuntu.com/4168-1/
- security.gentoo.org/glsa/202003-63
- seclists.org/bugtraq/2020/Feb/4
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MINU
- github.com/libidn/libidn2/compare/libidn2-2.1.0...libidn2-2.1.1
- cert-portal.siemens.com/productcert/html/ssa-398330.html
- github.com/advisories/GHSA-j2c9-63g7-697x
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MINU
- usn.ubuntu.com/4168-1
Elsewhere on this site
Related CVEs (same products)
- High CVE-2019-12290 GNU libidn2 before 2.2.0 fails to perform the roundtrip checks specified in RFC3490 Section 4.2... Oct 22, 2019
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No CISA SSVC assessment.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2019-18224 is "idn2_to_ascii_4i in lib/lookup.c in GNU libidn2 before 2.1.1 has a heap-based buffer overflow via...", rated Critical. It affects Libidn2 (Gnu); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.8 describes technical severity. EPSS 3.71% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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