GNU Tar through 1.30, when --sparse is used, mishandles file shrinkage during read access, which allows local users to cause a denial of service (infinite read loop in sparse_dump_region in sparse.c) by modifying a file that is supposed to be archived by a different user's process (e.g., a system backup running as root).
https://utcc.utoronto.ca/~cks/space/blog/sysadmin/TarFindingTruncateBug
https://twitter.com/thatcks/status/1076166645708668928
https://security.gentoo.org/glsa/201903-05
https://news.ycombinator.com/item?id=18745431
https://lists.debian.org/debian-lts-announce/2021/11/msg00025.html
https://lists.debian.org/debian-lts-announce/2018/12/msg00023.html
http://www.securityfocus.com/bid/106354
http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00077.html
http://lists.gnu.org/archive/html/bug-tar/2018-12/msg00023.html
http://git.savannah.gnu.org/cgit/tar.git/commit/?id=c15c42ccd1e2377945fd0414eca1a49294bff454
Published: 2018-12-26
Updated: 2021-11-30
Base Score: 1.9
Vector: CVSS2#AV:L/AC:M/Au:N/C:N/I:N/A:P
Severity: Low
Base Score: 4.7
Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Severity: Medium
Base Score: 9.3
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Severity: Critical