Description
libfyaml 0.9.6 contains a stack exhaustion vulnerability in fy_atom_iter_format(). When processing a specially crafted YAML document containing a very large literal or folded block scalar, the function repeatedly grows an internal buffer using alloca() inside a loop. The allocated stack memory is not released until the function returns, causing cumulative stack growth that can exceed the process stack limit and result in SIGSEGV and denial of service.
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 | libfyaml | No fix yet | — |
| Debian 13 | libfyaml | No fix yet | — |
| Debian 12 | libfyaml | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | libfyaml | No fix yet | — |
| Ubuntu 26.04 LTS | libfyaml | No fix yet | — |
| Ubuntu 24.04 LTS | libfyaml | No fix yet | — |
| Ubuntu 22.04 LTS | libfyaml | No fix yet | — |