CVE-2025-13601: Redhat Codeready Buffer Overflow Flaw

CVE-2025-13601 Overview

A heap-based buffer overflow vulnerability has been identified in GLib, the low-level core library that forms the foundation of GNOME and many Linux applications. The flaw exists in the g_escape_uri_string() function, where an incorrect calculation of buffer size can lead to an integer overflow when processing strings containing a very large number of characters requiring URI escaping.

When a specially crafted string with excessive unacceptable characters is passed to the vulnerable function, the length calculation for the escaped output string can overflow, resulting in an undersized buffer allocation. Subsequent write operations then extend beyond the allocated heap memory, potentially leading to memory corruption, application crashes, or in some scenarios, arbitrary code execution.

Critical Impact

This heap-based buffer overflow affects the widely-deployed GLib library, impacting numerous Red Hat Enterprise Linux distributions, OpenShift Container Platform deployments, and any application utilizing the vulnerable g_escape_uri_string() function for URI processing.

Affected Products

• GNOME GLib (core library)
• Red Hat Enterprise Linux for x86_64, ARM64, IBM z Systems, and Power (versions 8.x, 9.x, 10.x)
• Red Hat OpenShift Container Platform (versions 4.12, 4.16, 4.17, 4.18, 4.19)
• Red Hat CodeReady Linux Builder (multiple architectures and versions)
• Red Hat Ceph Storage 8.0
• Red Hat Discovery 2.0

Discovery Timeline

• November 26, 2025 - CVE-2025-13601 published to NVD
• March 19, 2026 - Last updated in NVD database

Technical Details for CVE-2025-13601

Vulnerability Analysis

The vulnerability resides in the g_escape_uri_string() function within GLib, which is responsible for escaping special characters in URI strings. The function calculates the required buffer size by counting characters that need escaping (each unacceptable character expands to three characters in the escaped form, e.g., a space becomes %20).

The integer overflow vulnerability is classified under CWE-190 (Integer Overflow or Wraparound). When the input string contains an exceptionally large number of characters requiring escape sequences, the multiplication operation used to calculate the output buffer size can wrap around, resulting in a much smaller value than actually needed. The subsequent memory allocation uses this corrupted size value, creating an undersized buffer on the heap.

As the function proceeds to write the escaped URI string, it writes beyond the allocated buffer boundaries, corrupting adjacent heap metadata or other heap-allocated data structures. This heap corruption can manifest as application crashes, denial of service, or potentially exploitable memory corruption scenarios.

Root Cause

The root cause is an integer overflow vulnerability in the buffer size calculation within g_escape_uri_string(). The function fails to properly validate that the calculated size for the escaped string will not exceed the maximum representable integer value. When multiplying the count of characters requiring escaping by the expansion factor, the result can exceed integer bounds and wrap to a small positive value, leading to insufficient memory allocation.

Attack Vector

Exploitation requires local access to the system. An attacker must be able to provide a malicious input string to an application that processes it through the vulnerable g_escape_uri_string() function. The attack string would need to contain an extremely large number of characters that require URI escaping, carefully calculated to trigger the integer overflow condition.

The attack flow involves:

1. Crafting a string with a calculated number of characters requiring URI escaping
2. Ensuring the total escaped length calculation overflows to a small positive integer
3. Triggering the application to process this string through g_escape_uri_string()
4. The undersized buffer is allocated on the heap
5. The escape operation writes beyond buffer boundaries, corrupting heap memory

Applications that accept user-controlled URI strings and process them through GLib's URI escaping functions are potential attack surfaces.

Detection Methods for CVE-2025-13601

Indicators of Compromise

• Unexpected application crashes or segmentation faults in applications using GLib for URI processing
• Memory corruption errors reported by system memory debugging tools (e.g., AddressSanitizer, Valgrind)
• Abnormal heap allocation patterns showing very small allocations followed by large write operations
• Core dumps from GLib-dependent applications showing corruption near g_escape_uri_string() call sites

Detection Strategies

• Monitor system logs for segmentation faults or SIGABRT signals from applications known to use GLib URI functions
• Deploy memory sanitizer tools in development and testing environments to catch buffer overflows early
• Implement application-level input validation to reject excessively large URI strings before processing
• Use runtime protection mechanisms that detect heap buffer overflows

Monitoring Recommendations

• Enable heap canary detection and stack smashing protection in production builds
• Configure core dump collection and analysis for GLib-dependent services
• Monitor for unusual memory allocation patterns in critical applications
• Set up alerts for application restart loops that may indicate exploitation attempts

How to Mitigate CVE-2025-13601

Immediate Actions Required

• Update GLib to the patched version provided by your Linux distribution
• Apply Red Hat security errata for affected Enterprise Linux and OpenShift deployments
• Implement input validation to limit URI string lengths before passing to GLib functions
• Consider temporary workarounds for systems that cannot be immediately patched

Patch Information

Red Hat has released multiple security advisories addressing this vulnerability across their product portfolio. Administrators should consult the appropriate advisory for their specific platform:

• Red Hat Security Advisory RHSA-2026:0936 - Initial patch release
• Red Hat Security Advisory RHSA-2026:1323 through RHSA-2026:1327 - Extended platform coverage
• Red Hat CVE Page for CVE-2025-13601 - Official vendor CVE information

The upstream fix is tracked in GNOME GitLab Merge Request #4914, which addresses the integer overflow in the buffer size calculation.

For technical details about the vulnerability, see GNOME GitLab Issue #3827.

Workarounds

• Implement application-level input validation to reject URI strings exceeding a safe maximum length before processing
• Deploy runtime memory protection tools such as AddressSanitizer in non-production environments for early detection
• Use application sandboxing or containerization to limit the impact of potential exploitation
• Consider temporary restrictions on user-supplied URI input in exposed services until patches can be applied

# Check installed GLib version on RHEL-based systems
rpm -qa | grep glib2

# Verify available security updates
yum check-update glib2

# Apply security updates
sudo yum update glib2

# For systems using dnf
sudo dnf update glib2