CVE-2015-1593

What it actually does

Incorrect data types in bitwise left-shift operations within randomize_stack_top and stack_maxrandom_size cause the Linux kernel's stack randomization on 64-bit platforms to produce insufficient entropy, allowing reliable prediction of the stack top address and bypassing ASLR.

Why it matters to the business

Older unpatched Linux systems remain exposed to memory-address prediction attacks that can facilitate further exploitation, potentially leading to unauthorized information disclosure or escalation in long-lived server and embedded deployments.

How an attack unfolds

An attacker first determines the target is running a vulnerable 64-bit kernel, then leverages the weakened randomization to calculate the stack base, enabling subsequent memory corruption or information-leak exploits that would otherwise be thwarted by ASLR.

How to fix it

Upgrade the Linux kernel to version 3.19.1 or later on all 64-bit platforms; rebuild and reboot affected systems with the corrected kernel binary.

How to confirm the fix worked

Verify the running kernel version is 3.19.1 or newer via uname -r; confirm the source files fs/binfmt_elf.c and arch/x86/mm/mmap.c contain the corrected data types for the shift operations.

Typical attack path

1. Fingerprint the remote or local system to confirm a pre-3.19.1 64-bit Linux kernel
2. Trigger or observe stack layout to obtain a predictable address range due to the shift-operation type error
3. Use the predicted stack location to bypass ASLR in a follow-on memory-safety exploit
4. Achieve information disclosure or code execution

How to detect it

Review system boot logs and package histories for kernels older than 3.19.1; look for post-exploitation artifacts such as unexpected memory mappings or failed ASLR-dependent exploit attempts in application logs.

What your security team should do

• Prioritize kernel upgrades on all internet-facing and multi-tenant 64-bit Linux hosts
• Enable additional kernel hardening features such as SMEP, SMAP, and KASLR where available
• Monitor EPSS and exploit-availability feeds for any resurgence in tooling targeting this class of ASLR bypass