In ng_pkt in transports/smart_pkt.c in libgit2 before 0.26.6 and 0.27.x before 0.27.4, a remote attacker can send a crafted smart-protocol "ng" packet that lacks a '\0' byte to trigger an out-of-bounds read that leads to DoS.
https://www.pro-linux.de/sicherheit/2/44650/denial-of-service-in-libgit2.html
https://lists.debian.org/debian-lts-announce/2022/03/msg00031.html
https://lists.debian.org/debian-lts-announce/2018/08/msg00024.html
https://github.com/libgit2/libgit2/releases/tag/v0.27.4
https://github.com/libgit2/libgit2/releases/tag/v0.26.6
https://github.com/libgit2/libgit2/commit/1f9a8510e1d2f20ed7334eeeddb92c4dd8e7c649