Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in Erlang OTP stdlib (erl tar module), hexpm hex core (hex erl tar module), hexpm hex (mix hex erl tar module) and erlang rebar3 (r3 hex erl tar module) allows an attacker who supplies a tar archive to cause a denial of service via a crafted GNU sparse member.

When erl tar:extract/1,2 writes a member to disk, erl tar:stream to file loop/3 reads it in chunks of 65536 bytes by default. For a GNU sparse member whose sparse map ends before its real size, erl tar:do sparse read/3 matches its trailing-hole clause before its zero-length clause. After the chunk is used up, the trailing-hole clause reads zero bytes, does not advance the position, and recurses forever. A 2048-byte archive keeps the extracting process and one scheduler busy until the process is killed. The {max size, N} option prevents this only when N is below the real size of the member. Extraction with the memory option is not affected.

hex core ships its own copy of erl tar as hex erl tar, and Hex and rebar3 ship hex core with prefixed module names (mix hex erl tar and r3 hex erl tar). These copies contain the same code and do not call stdlib's erl tar, so they are affected on any OTP version. OTP 28 is not affected, but an application running on OTP 28 is affected if it extracts archives through an affected version of hex core, Hex or rebar3.

This issue affects OTP from OTP 29.0 before OTP 29.1.2, corresponding to stdlib from 8.0 before 8.1.1, and rebar3 from 3.27.1 onward, and hex from 2.4.2 before 2.5.3; hex core: from 0.14.0 before 0.20.1.