Leptonica before 1.75.3 does not limit the number of characters in a %s format argument to fscanf or sscanf, which allows remote attackers to cause a denial of service (stack-based buffer overflow) or possibly have unspecified other impact via a long string, as demonstrated by the gplotRead and ptaReadStream functions.
https://security.gentoo.org/glsa/202312-01
https://lists.debian.org/debian-lts/2018/02/msg00054.html
https://lists.debian.org/debian-lts-announce/2018/03/msg00005.html
https://github.com/DanBloomberg/leptonica/commit/ee301cb2029db8a6289c5295daa42bba7715e99a