CVE-2018-9838

Bug description

The bigarray module in all recent ocaml versions is capable of reading in serialized (marshalled) objects from a external source which is often used for network operations and interprocess communication.

byterun/bigarray.c

Line 458 in ea60609

 b->data = malloc(elt_size * num_elts);

A integer overflow vulnerability allows under certain circumstances an remote attacker to input a corrupt object and edit arbitrary addresses in the processes memory which leads over common techniques (in this take libc one gadget but any rop gadget or got table vector would work) to arbitrary memory access (!) and in the course also arbitrary code execution

Please check the writeup.pdf for more details !!

In variations of this the exploit is usable in all ocaml versions we tested no matter if compiled to binary or intepreted (!)

Steps to reproduce

Check out the attached archive and run the makefile (or use the precompile executable) the exploit can be run by executing exploit.py (python2.7 and pwntools are required) The last step of code execution is using a one-gadget attack technique and is specific to the glibc version in use (e.g. tested is debian glibc 2.24-11+deb9u1) but can with minimal amount of work be ported to any libc version on any patch level to our knowledge

Of course you can also use the exploit.py to write your own version of exploit

Additional information

This Vulnerability in ocaml was discovered by me ([email protected]) and the exploit collaboratly developed with ([email protected]) For illustration purposes it was packaged as security challenge to demonstrate the impact of the issue (see writeup.pdf)

The caml_ba_deserialize function in byterun/bigarray.c in the standard library in OCaml 4.06.0 has an integer overflow which, in situations where marshalled data is accepted from an untrusted source, allows remote attackers to cause a denial of service (memory corruption) or possibly execute arbitrary code via a crafted object.

The caml_ba_deserialize function in byterun/bigarray.c in the standard library in OCaml 4.06.0 has an integer overflow which, in situations where marshalled data is accepted from an untrusted source, allows remote attackers to cause a denial of service (memory corruption) or possibly execute arbitrary code via a crafted object. (CVE-2018-9838)

These are all security issues fixed in the ocaml-4.12.1-1.1 package on the GA media of openSUSE Tumbleweed.

This update for ocaml fixes the following issues:

• CVE-2018-9838: Integer overflows when unmarshaling a bigarray data could result in a bigarray with impossibly large dimensions leading to overflow when computing the in-memory size of the bigarray. [bsc#1088591]

This update for ocaml fixes the following issues:

• CVE-2018-9838: Integer overflows when unmarshaling a bigarray data could result in a bigarray with impossibly large dimensions leading to overflow when computing the in-memory size of the bigarray. [bsc#1088591]

This update for ocaml fixes the following issues:

• CVE-2018-9838: The caml_ba_deserialize function in byterun/bigarray.c in the standard library had an integer overflow which, in situations where marshalled data is accepted from an untrusted source, allows remote attackers to cause a denial of service (memory corruption) or possibly execute arbitrary code via a crafted object. [bsc#1088591]

This update for ocaml fixes the following issues:

• CVE-2018-9838: The caml_ba_deserialize function in byterun/bigarray.c in the standard library had an integer overflow which, in situations where marshalled data is accepted from an untrusted source, allows remote attackers to cause a denial of service (memory corruption) or possibly execute arbitrary code via a crafted object. [bsc#1088591]

It was discovered that OCaml mishandled sign extensions. A remote attacker could use this vulnerability to steal sensitive information, cause a denial of service (crash), or possibly execute arbitrary code. This issue only affected Ubuntu 16.04 ESM. (CVE-2015-8869)

It was discovered that OCaml mishandled crafted input. An attacker could use this vulnerability to cause a denial of service or possibly execute arbitrary code. (CVE-2018-9838)