Bug 1565468 (CVE-2018-9838) - CVE-2018-9838 ocaml: Integer overflow in byterun/bigarray.c:caml_ba_deserialize() allows remote attackers to cause a denial of service or other unspecified impact
Summary: CVE-2018-9838 ocaml: Integer overflow in byterun/bigarray.c:caml_ba_deseriali...
Keywords:
Status: NEW
Alias: CVE-2018-9838
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1565470 1565471 1566999
Blocks: 1565476
TreeView+ depends on / blocked
 
Reported: 2018-04-10 05:20 UTC by Sam Fowler
Modified: 2020-12-17 10:39 UTC (History)
4 users (show)

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Description Sam Fowler 2018-04-10 05:20:22 UTC
The OCaml standard library in version 4.06.00 has an integer overflow vulnerability in byterun/bigarray.c:caml_ba_deserialize() when handling serialized (marshalled) data. A remote attacker could exploit this to cause a denial of service or possible code execution by supplying a crafted serialized object.


Upstream Issue:

https://caml.inria.fr/mantis/view.php?id=7765

Comment 1 Sam Fowler 2018-04-10 05:22:24 UTC
Created ocaml tracking bugs for this issue:

Affects: fedora-all [bug 1565471]

Comment 5 Richard W.M. Jones 2018-04-10 07:04:23 UTC
I think the impact of this should be "low".

My reasoning is that the Marshal interface is unsafe and should not
be used when sending data to untrusted end points.  The documentation
is quite explicit about this.

It is possible to crash the remote end point in multiple ways, eg:

let m = Marshal.to_string (1, 2) []
let x : bool * string = Marshal.from_string m 0
let () = Printf.printf "%b * %s" (fst x) (snd x)

$ ocamlopt crash.ml -o crash
$ ./crash 
Segmentation fault (core dumped)

OCaml provides ways to serialize data safely but Marshal is a low-level
interface which doesn't do that.

Of course I will fix this problem anyway in Fedora & RHEL.

Comment 6 Richard W.M. Jones 2018-04-11 11:57:02 UTC
They're still working on a fix upstream, but the latest proposal is
https://github.com/ocaml/ocaml/pull/1718


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