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vulnerability note CVE-2013-7439

libX11: buffer overflow of MakeBigReq

Synthesis of the vulnerability

An attacker can generate a buffer overflow in applications using MakeBigReq() of libX11, in order to trigger a denial of service, and possibly to execute code.
Vulnerable products: Debian, Solaris, Ubuntu, libX11.
Severity of this weakness: 2/4.
Consequences of a hack: user access/rights, denial of service on service.
Hacker's origin: user shell.
Creation date: 08/04/2015.
Références of this bulletin: 56508, bulletinjul2015, CVE-2013-7439, DSA-3224-1, USN-2568-1, VIGILANCE-VUL-16554.

Description of the vulnerability

The libX11 library uses the MakeBigReq() macro to extend a query.

However, this macro performs a memmove() on 4 bytes past the buffer end. An overflow thus occurs.

An attacker can therefore generate a buffer overflow in applications using MakeBigReq() of libX11, in order to trigger a denial of service, and possibly to execute code.
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