CVE-2025-13654: Zevv Duc Buffer Overflow Vulnerability

CVE-2025-13654 Overview

A stack buffer overflow vulnerability exists in the buffer_get function of duc, a disk management tool developed by Zevv. The vulnerability occurs due to a logic error in a boundary condition check that can evaluate to true due to integer underflow, allowing an out-of-bounds read operation. This flaw enables attackers to trigger memory corruption through crafted input, potentially leading to denial of service conditions.

Critical Impact

Network-accessible stack buffer overflow in duc allows remote attackers to cause denial of service through out-of-bounds memory read operations.

Affected Products

• Zevv Duc (versions prior to 1.4.6)

Discovery Timeline

• 2025-12-05 - CVE CVE-2025-13654 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2025-13654

Vulnerability Analysis

The vulnerability resides in the buffer_get function within src/libduc/buffer.c. The function is responsible for reading data from a buffer structure, but contains a critical logic flaw in its boundary checking mechanism. The original condition b->ptr <= b->len - len is mathematically incorrect when b->len is less than len, causing an integer underflow. When this underflow occurs, the subtraction wraps around to a large positive value, making the condition evaluate to true even when there isn't sufficient data in the buffer to read.

This allows the subsequent memcpy operation to read beyond the allocated buffer boundaries, resulting in an out-of-bounds read. The vulnerability is classified as CWE-787 (Out-of-bounds Write), though the immediate impact manifests as an out-of-bounds read that can corrupt stack memory or cause application crashes.

Root Cause

The root cause is an arithmetic logic error in the boundary condition check within buffer_get. The original expression b->ptr <= b->len - len performs subtraction before comparison, which can underflow when b->len is smaller than len. The corrected expression b->ptr + len <= b->len properly adds the requested length to the current pointer position before comparing against the buffer length, avoiding any underflow conditions.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can craft malicious input that triggers the buffer_get function with parameters that cause the underflow condition. When the boundary check incorrectly passes, the function performs an out-of-bounds memory read, which can lead to application crash or denial of service. The attack does not require any privileges and has low complexity to execute.

// Vulnerable code in src/libduc/buffer.c (before patch)
static int buffer_get(struct buffer *b, void *data, size_t len)
{
	if(b->ptr <= b->len - len) {  // Vulnerable: underflow when b->len < len
		memcpy(data, b->data + b->ptr, len);
		b->ptr += len;
		return len;

Source: GitHub Commit 8638c436

// Fixed code in src/libduc/buffer.c (after patch)
static int buffer_get(struct buffer *b, void *data, size_t len)
{
	if(b->ptr + len <= b->len) {  // Fixed: no underflow possible
		memcpy(data, b->data + b->ptr, len);
		b->ptr += len;
		return len;

Source: GitHub Commit 8638c436

Detection Methods for CVE-2025-13654

Indicators of Compromise

• Unexpected crashes or segmentation faults in duc processes
• Abnormal memory access patterns in duc application logs
• Core dumps indicating out-of-bounds memory operations in buffer_get

Detection Strategies

• Monitor for duc process crashes with stack traces referencing buffer_get or buffer.c
• Implement application-level logging to detect malformed input that could trigger the vulnerability
• Use memory sanitizers (ASan, Valgrind) during development and testing to catch out-of-bounds access

Monitoring Recommendations

• Enable crash monitoring and core dump collection for duc processes in production environments
• Review system logs for recurring duc crashes that may indicate exploitation attempts
• Deploy endpoint detection solutions capable of identifying memory corruption attacks

How to Mitigate CVE-2025-13654

Immediate Actions Required

• Upgrade duc to version 1.4.6 or later immediately
• If upgrade is not immediately possible, consider temporarily disabling duc or restricting network access to the service
• Review system logs for any signs of exploitation attempts

Patch Information

The vulnerability has been fixed in duc version 1.4.6. The patch corrects the logic error in the buffer_get function by changing the boundary condition from b->ptr <= b->len - len to b->ptr + len <= b->len, which eliminates the integer underflow condition. The fix is available in GitHub Release 1.4.6 and the specific commit can be reviewed at GitHub Commit 8638c436. Additional details are available in the CERT Vulnerability Advisory #441887.

Workarounds

• Restrict network access to duc services using firewall rules until patching is complete
• Run duc processes with minimal privileges to limit potential impact
• Implement network segmentation to isolate systems running vulnerable duc versions

# Upgrade duc to patched version
git clone https://github.com/zevv/duc.git
cd duc
git checkout 1.4.6
./configure && make && sudo make install