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CVE-2018-14618: On systems with a 32 bit size_t, the math to calculate SUM triggers an integer overflow when the password…

CVE-2018-14618 is rated critical with a CVSS v3.0 base score of 9.8 and NVD lists 4 affected products, including Haxx Libcurl. Per its scoring, it can be exploited over the network, without authentication, without any user interaction. The scored impact on confidentiality, integrity and availability is the highest available.

Vulnerability description

curl before version 7.61.1 is vulnerable to a buffer overrun 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 CVE-2017-8816.)

Severity breakdown

CVSS v3.0 9.8: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack vector: Network. Exploitable remotely over the network, with no need for local or physical access.
Attack complexity: Low. No special conditions; the attack can be repeated reliably.
Privileges required: None. No account or prior access is needed.
User interaction: None. No action from any user is needed.
Scope: Unchanged. Impact stays within the vulnerable component.
Confidentiality impact: High. Total loss of confidentiality; sensitive data can be fully disclosed.
Integrity impact: High. Total loss of integrity; data or system state can be fully modified.
Availability impact: High. Total loss of availability; the component can be shut down.

Underlying weakness

CWE-122: Heap-based Buffer Overflow

The product writes past the end of a buffer that was allocated on the heap.

CWE-131: Incorrect Calculation of Buffer Size

The product does not correctly calculate the size to be used when allocating a buffer.

CWE-190: Integer Overflow or Wraparound

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

Affected products

Haxx Libcurl: before 7.61.1
Canonical Ubuntu Linux: 12.04; 14.04; 16.04; 18.04
Debian Linux: 9.0
Red Hat Enterprise Linux: 6.0; 7.0; 7.4; 7.5; 7.6