CVE Vulnerabilities

CVE-2018-1000030

Out-of-bounds Write

Published: Feb 08, 2018 | Modified: Aug 24, 2020
CVSS 3.x
3.6
LOW
Source:
NVD
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:L
CVSS 2.x
3.3 LOW
AV:L/AC:M/Au:N/C:P/I:N/A:P
RedHat/V2
RedHat/V3
3.6 LOW
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:L
Ubuntu

Python 2.7.14 is vulnerable to a Heap-Buffer-Overflow as well as a Heap-Use-After-Free. Python versions prior to 2.7.14 may also be vulnerable and it appears that Python 2.7.17 and prior may also be vulnerable however this has not been confirmed. The vulnerability lies when multiply threads are handling large amounts of data. In both cases there is essentially a race condition that occurs. For the Heap-Buffer-Overflow, Thread 2 is creating the size for a buffer, but Thread1 is already writing to the buffer without knowing how much to write. So when a large amount of data is being processed, it is very easy to cause memory corruption using a Heap-Buffer-Overflow. As for the Use-After-Free, Thread3->Malloc->Thread1->Free’s->Thread2-Re-uses-Free’d Memory. The PSRT has stated that this is not a security vulnerability due to the fact that the attacker must be able to run code, however in some situations, such as function as a service, this vulnerability can potentially be used by an attacker to violate a trust boundary, as such the DWF feels this issue deserves a CVE.

Weakness

The software writes data past the end, or before the beginning, of the intended buffer.

Affected Software

Name Vendor Start Version End Version
Python Python * 2.7.14
Python2.7 Ubuntu artful *
Python2.7 Ubuntu esm-infra/xenial *
Python2.7 Ubuntu precise/esm *
Python2.7 Ubuntu trusty *
Python2.7 Ubuntu trusty/esm *
Python2.7 Ubuntu xenial *

Potential Mitigations

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

  • For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

  • Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

  • Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.

  • Run or compile the software using features or extensions that automatically provide a protection mechanism that mitigates or eliminates buffer overflows.

  • For example, certain compilers and extensions provide automatic buffer overflow detection mechanisms that are built into the compiled code. Examples include the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice.

  • Consider adhering to the following rules when allocating and managing an application’s memory:

  • Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

  • Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64].

References