CVE-2016-20044: PInfo Buffer Overflow Vulnerability

CVE-2016-20044 Overview

CVE-2016-20044 is a local buffer overflow vulnerability affecting PInfo version 0.6.9-5.1. PInfo is a console-based hypertext info file viewer commonly used on Linux systems to browse GNU info documentation. The vulnerability allows local attackers to execute arbitrary code by supplying an oversized argument to the -m parameter. This classic buffer overflow enables attackers to craft malicious input strings with 564 bytes of padding followed by a carefully constructed return address to overwrite the instruction pointer and redirect execution flow to attacker-controlled shellcode.

Critical Impact

Local attackers can achieve arbitrary code execution with the privileges of the user running PInfo, potentially leading to system compromise or privilege escalation when combined with other vulnerabilities.

Affected Products

• PInfo 0.6.9-5.1

Discovery Timeline

• 2026-03-28 - CVE CVE-2016-20044 published to NVD
• 2026-03-30 - Last updated in NVD database

Technical Details for CVE-2016-20044

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-bounds Write), a memory corruption issue that occurs when PInfo fails to properly validate the length of input supplied to the -m parameter before copying it to a fixed-size stack buffer. When an attacker provides input exceeding the buffer's allocated size, the excess data overwrites adjacent stack memory, including the saved return address.

The exploitation technique leverages the lack of boundary checking on user-supplied input. By precisely calculating the offset (564 bytes of padding), an attacker can position a controlled return address at the exact location of the saved instruction pointer on the stack. When the vulnerable function returns, execution jumps to the attacker's specified address, which can point to embedded shellcode or return-oriented programming (ROP) gadgets.

Root Cause

The root cause of this vulnerability is improper input validation in the -m parameter handling code. The application uses an unsafe memory copy operation (likely strcpy() or similar) without first verifying that the source data fits within the destination buffer's boundaries. This oversight allows unbounded user input to overflow the allocated stack buffer.

Attack Vector

The attack vector is local, requiring the attacker to have access to execute the PInfo binary on the target system. The exploitation process involves:

1. Crafting a malicious input string with precisely 564 bytes of padding
2. Appending a return address that points to attacker-controlled shellcode
3. Executing PInfo with the malicious payload via the -m parameter
4. The overflow overwrites the saved return address on the stack
5. Upon function return, execution redirects to the attacker's shellcode

The vulnerability can be triggered via command line execution, making it exploitable in scenarios where an attacker has local shell access or can influence PInfo invocation through scripts or other programs.

Detection Methods for CVE-2016-20044

Indicators of Compromise

• Unusual PInfo process crashes or segmentation faults in system logs
• Execution of PInfo with abnormally long -m parameter arguments (greater than 564 bytes)
• Unexpected child processes spawned from PInfo execution
• Anomalous shell activity originating from PInfo process context

Detection Strategies

• Monitor process execution for PInfo invocations with unusually long command-line arguments
• Deploy application crash monitoring to detect segmentation faults in PInfo
• Implement audit logging for local command execution patterns
• Use memory protection tools (ASLR, stack canaries) to detect exploitation attempts

Monitoring Recommendations

• Enable auditd rules to log PInfo executions and their command-line parameters
• Configure crash dump analysis to capture PInfo segmentation faults for forensic review
• Monitor for suspicious process lineage where PInfo spawns unexpected child processes
• Review system authentication logs for anomalous local access patterns

How to Mitigate CVE-2016-20044

Immediate Actions Required

• Upgrade PInfo to a patched version if available from your distribution's package repository
• Remove or restrict access to the PInfo binary if not required for operations
• Implement execution controls to limit which users can run PInfo
• Enable stack protection mechanisms (ASLR, NX bit, stack canaries) on the system

Patch Information

Security teams should check with their Linux distribution for patched versions of PInfo. Additional information is available through the following resources:

• Debian Pinfo Information
• Vulncheck Advisory on Pinfo
• Exploit-DB #40023 provides technical details on the exploitation technique

Workarounds

• Remove or uninstall PInfo from systems where it is not required
• Restrict execution permissions on the PInfo binary to trusted users only
• Use alternative info file viewers such as info from GNU Texinfo
• Implement mandatory access control policies (SELinux/AppArmor) to contain PInfo execution
• Enable address space layout randomization (ASLR) and non-executable stack protections as defense-in-depth measures