Quantum Secular Labs / Blog / Advisories

CVE-2016-5769: PHP: Buffer overflow

CVE-2016-5769 is rated critical with a CVSS v3.0 base score of 9.8 and affects PHP. 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

Multiple integer overflows in mcrypt.c in the mcrypt extension in PHP before 5.5.37, 5.6.x before 5.6.23, and 7.x before 7.0.8 allow remote attackers to cause a denial of service (heap-based buffer overflow and application crash) or possibly have unspecified other impact via a crafted length value, related to the (1) mcrypt_generic and (2) mdecrypt_generic functions.

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-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

  • PHP: up to and including 5.5.36; 5.6.0 alpha1; 5.6.0 alpha2; 5.6.0 alpha3; 5.6.0 alpha4; 5.6.0 alpha5; 5.6.0 beta1; 5.6.0 beta2; 5.6.0 beta3; 5.6.0 beta4; 5.6.1; 5.6.2

References