Affected: Arm Ltd Arm GNU Toolchain, GNU GCC

**DISPUTED**A failure in the -fstack-protector feature in GCC-based toolchains that target AArch64 allows an attacker to exploit an existing buffer overflow in dynamically-sized local variables in your application without this being detected. This stack-protector failure only applies to C99-style dynamically-sized local variables or those created using alloca(). The stack-protector operates as intended for statically-sized local variables.

The default behavior when the stack-protector detects an overflow is to terminate your application, resulting in controlled loss of availability. An attacker who can exploit a buffer overflow without triggering the stack-protector might be able to change program flow control to cause an uncontrolled loss of availability or to go further and affect confidentiality or integrity. NOTE: The GCC project argues that this is a missed hardening bug and not a vulnerability by itself.

Affected: Ubuntu:Pro:20.04:LTS: gcc-10, Ubuntu:22.04:LTS: gcc-10, Ubuntu:22.04:LTS: gcc-11, Ubuntu:22.04:LTS: gcc-12

It was discovered that the -fstack-protector hardening feature in GCC for AArch64 did not properly protect dynamically-sized local variables such as those created using C99 variable length arrays or alloca. As a result, an attacker who was able to trigger a buffer overflow in such cases could bypass the intended stack protection checks. (CVE-2023-4039)