CVE-2026-0988: GLib Buffer Overflow DoS Vulnerability

CVE-2026-0988 Overview

A flaw was found in GLib where missing validation of offset and count parameters in the g_buffered_input_stream_peek() function can lead to an integer overflow during length calculation. When specially crafted values are provided, this overflow results in an incorrect size being passed to memcpy(), triggering a buffer overflow. This vulnerability can cause application crashes, leading to a Denial of Service (DoS) condition.

Critical Impact

Applications using GLib's buffered input stream functionality may crash when processing maliciously crafted input, causing service disruption.

Affected Products

• GLib library (all versions with vulnerable g_buffered_input_stream_peek() implementation)
• Applications utilizing GLib buffered input stream functionality
• Linux distributions shipping affected GLib versions

Discovery Timeline

• 2026-01-21 - CVE-2026-0988 published to NVD
• 2026-01-21 - Last updated in NVD database

Technical Details for CVE-2026-0988

Vulnerability Analysis

This vulnerability is classified as CWE-190 (Integer Overflow or Wraparound). The flaw exists in the g_buffered_input_stream_peek() function within GLib, a widely-used low-level core library that provides data structure handling, portability wrappers, and interfaces for runtime functionality.

The vulnerable function fails to properly validate the offset and count parameters before performing arithmetic operations. When an attacker supplies carefully crafted values for these parameters, the length calculation can overflow, wrapping around to a much smaller value. This incorrect size is then passed to memcpy(), which attempts to copy data beyond the allocated buffer boundaries.

The attack requires network access but has high complexity to exploit successfully. No privileges are required, and no user interaction is needed. The impact is limited to availability, with no direct effect on confidentiality or integrity.

Root Cause

The root cause is improper input validation in the g_buffered_input_stream_peek() function. The function does not adequately validate that the offset and count parameters, when combined, will not exceed the maximum representable integer value. This lack of bounds checking allows an integer overflow to occur during the internal length calculation, which subsequently causes a buffer overflow when memcpy() operates with the incorrect (wrapped) size value.

Attack Vector

The vulnerability is exploitable over the network, though exploitation requires high complexity. An attacker must be able to influence the parameters passed to g_buffered_input_stream_peek() through application-specific input vectors. The attack chain typically involves:

1. Identifying an application that uses GLib's GBufferedInputStream class
2. Finding an input path where user-controlled data influences the offset or count parameters
3. Crafting input that causes the integer overflow during length calculation
4. Triggering the buffer overflow via the corrupted memcpy() size, causing application crash

The vulnerability mechanism involves the arithmetic overflow when calculating buffer sizes. When the offset and count values are manipulated to cause an integer wrap, the resulting smaller-than-expected size passed to memcpy() leads to memory corruption. For detailed technical information, see the Red Hat CVE-2026-0988 Advisory and Red Hat Bug Report #2429886.

Detection Methods for CVE-2026-0988

Indicators of Compromise

• Unexpected application crashes in processes using GLib buffered input streams
• Core dumps showing crashes within g_buffered_input_stream_peek() or related memcpy() operations
• Abnormal network traffic patterns preceding application crashes
• System logs indicating segmentation faults in GLib-dependent applications

Detection Strategies

• Monitor for application crashes with stack traces referencing g_buffered_input_stream_peek() or GBufferedInputStream
• Implement runtime memory protection tools such as AddressSanitizer (ASan) to detect buffer overflows during testing
• Use static analysis tools to identify potential integer overflow conditions in code paths that call vulnerable GLib functions
• Deploy intrusion detection systems to identify anomalous input patterns targeting affected applications

Monitoring Recommendations

• Enable crash reporting and log aggregation for applications dependent on GLib
• Monitor system stability metrics for applications using buffered input stream functionality
• Implement application-level logging around input stream operations for forensic analysis
• Set up alerts for repeated crashes or service restarts in affected applications

How to Mitigate CVE-2026-0988

Immediate Actions Required

• Identify all systems running applications that depend on GLib's buffered input stream functionality
• Review vendor security advisories from your Linux distribution for GLib updates
• Prioritize patching based on network exposure of affected applications
• Consider implementing input validation at the application layer as an additional defense

Patch Information

Consult the Red Hat CVE-2026-0988 Advisory for official patch information and updates. Additional details are available in Red Hat Bug Report #2429886. Check with your Linux distribution vendor for package updates addressing this vulnerability.

Workarounds

• Implement application-level input validation to reject unreasonably large offset or count values before they reach GLib functions
• Use network-level controls to limit exposure of affected applications to untrusted networks
• Deploy application sandboxing or containerization to limit the impact of potential crashes
• Consider implementing rate limiting on input streams to reduce the attack surface

# Check installed GLib version on Debian/Ubuntu systems
dpkg -l | grep libglib

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

# Monitor for crashes in GLib-dependent applications
journalctl -f | grep -i "segfault\|g_buffered"