Description
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.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | libidn2 | 2.2.0-1 | — |
| Debian 13 | libidn2 | 2.2.0-1 | — |
| Debian 12 | libidn2 | 2.2.0-1 | — |
| Debian 10 | libidn2 | 2.0.5-1+deb10u1 | DSA-4613-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | libidn2 | 2.0.4-1.1ubuntu0.2 | USN-4168-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 16.04 LTS | libidn2-0 | No fix yet | — |
| Ubuntu Pro 14.04 LTS | libidn2-0 | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | idn2 +2 | 2.2.0-1.el8 | RHBA-2019:3621 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | idn2 +2 | 2.2.0-1.el8 | ALBA-2019:3621 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP1 | libidn2 | 2.2.0-3.3.1 | SUSE-SU-2019:3086-1 |
| SLES 15 | libidn2 | 2.2.0-3.3.1 | SUSE-SU-2019:3086-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 15.1 | libidn2 | 2.2.0-lp151.3.3.1 | openSUSE-SU-2019:2611-1 |
| openSUSE Leap 15.0 | libidn2 | 2.2.0-lp150.2.3.1 | openSUSE-SU-2019:2613-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.23 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.22 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.21 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.20 | libidn2 | 2.1.1-r0 | — |
Show 8 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.18 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.17 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.16 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.15 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.14 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.13 | libidn2 | 2.1.1-r0 | — |
| Alpine v3.12 | libidn2 | 2.1.1-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | idn2 +2 | 2.3.0-1.amzn2 | ALAS2-2019-1373 |
Advisories 10
- ALBA-2019:3621 libidn2 bug fix and enhancement update AlmaLinux Security Advisories · Oct 29, 2026
- RHBA-2019:3621 Red Hat Bug Fix Advisory: libidn2 bug fix and enhancement update Red Hat Security Advisories (RHSA) · Oct 14, 2026
- SSA-398330 SSA-398330: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP >= V3.1.0 and < V3.1.5 Siemens ProductCERT · Oct 13, 2026
- USN-4168-1 libidn2 vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- DSA-4613-1 libidn2 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- openSUSE-SU-2019:2613-1 Security update for libidn2 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2019:3086-1 Security update for libidn2 SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2019:2611-1 Security update for libidn2 SUSE / openSUSE Security Updates · Feb 4, 2026
- ICSA-23-348-10 Siemens SIMATIC S7-1500 CISA ICS & IT advisories · Aug 12, 2025
- ALAS2-2019-1373 Moderate: libidn2 security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Dec 18, 2019
References
- https://github.com/libidn/libidn2/compare/libidn2-2.1.0...libidn2-2.1.1
- https://github.com/libidn/libidn2/commit/e4d1558aa2c1c04a05066ee8600f37603890ba8c
- https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=12420
- USN-4168-1 vendor-advisory
- FEDORA-2019-a8d35fcf7c vendor-advisory
- FEDORA-2019-d3221d69e0 vendor-advisory
- openSUSE-SU-2019:2611 vendor-advisory
- openSUSE-SU-2019:2613 vendor-advisory
- DSA-4613 vendor-advisory
- 20200203 [SECURITY] [DSA 4613-1] libidn2 security update mailing-list
- GLSA-202003-63 vendor-advisory