Description
A NULL pointer dereference is present in libyang before v1.0-r3 in the function lys_extension_instances_free() due to a copy of unresolved extensions in lys_restr_dup(). Applications that use libyang to parse untrusted input yang files may crash.
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 | libyang | 1.0.176-1 | — |
| Debian 13 | libyang | 1.0.176-1 | — |
| Debian 10 | libyang | 0.16.105+really1.0-0+deb10u1 | DLA-3572-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | libyang | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | libyang | 1.0.184-1.el8 | RHEA-2021:1906 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | libyang | 1.0.184-1.el8 | ALEA-2021:1906 |
Advisories 3
- ALEA-2021:1906 libyang bug fix and enhancement update AlmaLinux Security Advisories · Oct 29, 2026
- DLA-3572-1 libyang - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RHEA-2021:1906 Red Hat Enhancement Advisory: libyang bug fix and enhancement update Red Hat Security Advisories (RHSA) · Nov 22, 2025
References
- https://github.com/CESNET/libyang/compare/v1.0-r2...v1.0-r3
- https://github.com/CESNET/libyang/commit/7852b272ef77f8098c35deea6c6f09cb78176f08
- https://github.com/CESNET/libyang/issues/773
- https://bugzilla.redhat.com/show_bug.cgi?id=1793935
- [debian-lts-announce] 20230919 [SECURITY] [DLA 3572-1] libyang security update mailing-list