CVE-2026-22190: Panda3D Information Disclosure Vulnerability

CVE-2026-22190 Overview

CVE-2026-22190 is a format string vulnerability in Panda3D's egg-mkfont utility that allows attackers to disclose stack-resident memory and pointer values. The vulnerability exists in versions up to and including 1.10.16, where the -gp (glyph pattern) command-line option is passed directly as the format string argument to sprintf() with only a single argument supplied. This allows an attacker who can control the command-line input to inject additional format specifiers, causing the utility to read unintended stack values and write the formatted output into generated .egg and .png files.

Critical Impact

Attackers can leverage this format string vulnerability to extract sensitive stack memory contents, including pointer values, potentially aiding in further exploitation or bypass of security mechanisms like ASLR.

Affected Products

• Panda3D versions up to and including 1.10.16
• Panda3D egg-mkfont utility

Discovery Timeline

• 2026-01-07 - CVE CVE-2026-22190 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2026-22190

Vulnerability Analysis

This vulnerability falls under CWE-134 (Use of Externally-Controlled Format String), a well-known class of security issues in C/C++ applications. The egg-mkfont tool, which is used to generate font assets for the Panda3D game engine, accepts a -gp parameter to define glyph patterns. This user-controlled input is passed directly to sprintf() as the format string without proper sanitization.

When an attacker includes format specifiers such as %x, %p, or %s in the -gp argument, the function reads additional values from the stack that were never intended to be accessed. The resulting formatted output is then written to the generated .egg and .png files, effectively embedding leaked memory contents into the output files.

The attack requires local access to execute the vulnerable utility with malicious arguments. While this limits the attack surface, it poses risks in environments where untrusted users can execute build tools or where automated build pipelines process untrusted input.

Root Cause

The root cause is the direct use of user-supplied input as a format string argument to sprintf(). The vulnerable code pattern passes the -gp command-line option value directly to sprintf() without any validation or sanitization. Secure coding practices dictate that format strings should always be static, with user input passed only as arguments to format specifiers.

The proper fix would involve using a static format string such as sprintf(buffer, "%s", user_input) instead of sprintf(buffer, user_input), or employing safer string handling functions altogether.

Attack Vector

The attack vector is local, requiring the attacker to have the ability to execute the egg-mkfont binary with crafted command-line arguments. An attacker would invoke the utility with format specifiers embedded in the -gp parameter value. For example, specifying patterns containing %x or %p format specifiers would cause the function to interpret subsequent stack values as arguments to format, leaking their contents into the output files.

The leaked information could include:

• Stack pointer values that reveal memory layout
• Return addresses useful for bypassing ASLR
• Other sensitive data residing on the stack

This information disclosure could serve as a stepping stone for more sophisticated attacks if combined with other vulnerabilities.

Detection Methods for CVE-2026-22190

Indicators of Compromise

• Unusual command-line arguments passed to egg-mkfont containing format specifiers like %x, %p, %n, or %s
• Generated .egg or .png files containing unexpected hexadecimal values or memory addresses
• Process execution logs showing egg-mkfont invoked with suspicious -gp parameter patterns
• Audit logs indicating repeated execution of egg-mkfont with varying format string patterns

Detection Strategies

• Monitor process execution for egg-mkfont with command-line arguments containing percent signs followed by format characters
• Implement file integrity monitoring on build output directories to detect anomalous content in generated files
• Deploy endpoint detection rules that flag command-line patterns matching format string exploitation attempts
• Review build logs and CI/CD pipeline outputs for unexpected egg-mkfont invocations

Monitoring Recommendations

• Enable command-line auditing on systems where Panda3D development tools are installed
• Implement application whitelisting to control execution of development utilities
• Monitor for new or modified .egg and .png files in unexpected locations
• Set up alerts for process executions with anomalous argument patterns

How to Mitigate CVE-2026-22190

Immediate Actions Required

• Upgrade Panda3D to a patched version when available from the vendor
• Restrict execution permissions for egg-mkfont to trusted development users only
• Audit any automated build processes that invoke egg-mkfont with external input
• Review and sanitize any input sources that may supply the -gp parameter value

Patch Information

A security update addressing this vulnerability has been disclosed. Refer to the VulnCheck Advisory and the Full Disclosure Post for detailed patch information. Users should upgrade to the latest available version of Panda3D from the official website or the GitHub repository.

Workarounds

• Avoid using the -gp option with any untrusted or user-controlled input
• Wrap egg-mkfont execution in a script that validates and sanitizes the -gp parameter before passing it to the utility
• Run egg-mkfont in a sandboxed or containerized environment to limit potential information disclosure impact
• Use file permission controls to prevent unauthorized users from executing the vulnerable utility

# Restrict egg-mkfont execution permissions
chmod 750 /path/to/panda3d/bin/egg-mkfont
chown root:developers /path/to/panda3d/bin/egg-mkfont