NTLM password overflow via integer overflow
Project curl Security Advisory, September 5th 2018 -
libcurl contains a buffer overflow in the NTLM authentication code.
The internal function `Curl_ntlm_core_mk_nt_hash` multiplies the `length` of
the password by two (SUM) to figure out how large temporary storage area to
allocate from the heap.
The `length` value is then subsequently used to iterate over the password and
generate output into the allocated storage buffer. On systems with a 32 bit
`size_t`, the math to calculate SUM triggers an integer overflow when the
password length exceeds 2GB (2^31 bytes). This integer overflow usually causes
a very small buffer to actually get allocated instead of the intended very
huge one, making the use of that buffer end up in a heap buffer overflow.
(This bug is almost identical to
We are not aware of any exploit of this flaw.
This bug was introduced in commit
[be285cde3f](https://github.com/curl/curl/commit/be285cde3f), April 2006.
The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2018-XXXX to this issue.
CWE-131: Incorrect Calculation of Buffer Size
This is only an issue on 32 bit systems. It also requires the password field
to use more than 2GB of memory, which in itself should be rare.
- Affected versions: libcurl 7.15.4 to and including 7.61.0
- Not affected versions: libcurl < 7.15.4 and >= 7.61.1
curl is used by many applications, but not always advertised as such.
In libcurl version 7.61.1, the integer overflow is avoided.
A [patch for CVE-2018-XXXX](https://curl.haxx.se/CVE-2018-bf5f.patch) is
We suggest you take one of the following actions immediately, in order of
A - Upgrade curl to version 7.61.1
B - Apply the patch to your version and rebuild
C - Put length restrictions on the password you can pass to libcurl
It was [publicly reported](https://github.com/curl/curl/issues/2756) to the
curl project on July 18, 2018. We contacted distros@openwall on August 27.
curl 7.61.1 was released on September 5 2018, coordinated with the publication
of this advisory.
Reported by Zhaoyang Wu. Patch by Daniel Stenberg.
No dice using a crafted .netrc or inputting large values in the password prompt that pops up if -u is passed in.
Tried triggering this directly via setting a 2GB password through libcurl (res = curl_easy_setopt(curl, CURLOPT_PASSWORD, pass) on a 32-bit system. Unfortunately, curl_easy_setopt for CURLOPT_PASSWORD does a strdup, which naturally fails. Curl then returns out of memory before hitting the target code.
So this flaw may be possible to hit on 32-bit, but I'm unclear how. There needs to be a code path that directly takes user input without copying it. May exist, but I've looked down five or so avenues and haven't found it yet.
The code does show a pretty trivial heap overflow, but getting there seems mildly difficult.
Name: the Curl project
Upstream: Zhaoyang Wu
Created curl tracking bugs for this issue:
Affects: fedora-all [bug 1625563]
This issue has been addressed in the following products:
Red Hat Software Collections for Red Hat Enterprise Linux 6
Red Hat Software Collections for Red Hat Enterprise Linux 7
Red Hat Software Collections for Red Hat Enterprise Linux 7.4 EUS
Red Hat Software Collections for Red Hat Enterprise Linux 7.5 EUS
Red Hat Software Collections for Red Hat Enterprise Linux 7.6 EUS
Via RHSA-2018:3558 https://access.redhat.com/errata/RHSA-2018:3558
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):