CVE-2025-2174: Zapping-vbi Zvbi RCE Vulnerability

CVE-2025-2174 Overview

A vulnerability has been identified in libzvbi versions up to 0.2.43, affecting the vbi_strndup_iconv_ucs2 function within the src/conv.c file. This integer overflow vulnerability allows remote attackers to manipulate the src_length argument, potentially leading to heap memory corruption. The exploit has been publicly disclosed and may be actively used in the wild.

Critical Impact

Remote attackers can exploit the integer overflow in vbi_strndup_iconv_ucs2 to cause heap overflow conditions, potentially leading to denial of service or memory corruption in applications utilizing the libzvbi library.

Affected Products

• zapping-vbi zvbi versions up to 0.2.43
• Applications and systems utilizing the libzvbi library for VBI (Vertical Blanking Interval) processing
• Linux distributions packaging vulnerable versions of zvbi

Discovery Timeline

• 2025-03-11 - CVE-2025-2174 published to NVD
• 2025-10-03 - Last updated in NVD database

Technical Details for CVE-2025-2174

Vulnerability Analysis

This vulnerability stems from an integer overflow condition in the vbi_strndup_iconv_ucs2 function located in src/conv.c. The function handles character set conversion operations and fails to properly validate the src_length parameter before performing arithmetic operations. When a maliciously crafted src_length value is supplied, the integer overflow can result in an undersized buffer allocation, which subsequently leads to heap overflow conditions when data is written to this buffer.

The vulnerability is exploitable remotely, as the affected function processes input that can originate from network sources. Applications using libzvbi for processing VBI data streams from untrusted sources are particularly at risk.

Root Cause

The root cause is improper validation of the src_length argument in the vbi_strndup_iconv_ucs2 function. The function performs arithmetic operations on this value without checking for potential integer overflow conditions. When the input size is excessively large, the calculation wraps around, resulting in a smaller-than-expected buffer allocation. Subsequent memory operations then write beyond the allocated buffer boundaries.

Additionally, similar integer overflow conditions were found in src/io-sim.c and src/search.c, where buffer capacity calculations could overflow during extension operations.

Attack Vector

The attack is network-accessible and can be launched remotely without requiring authentication or user interaction. An attacker can supply specially crafted data to an application utilizing libzvbi, triggering the integer overflow in the affected function. The manipulation of the src_length parameter causes the library to allocate an insufficient buffer, leading to heap corruption when the conversion operation writes beyond the buffer boundaries.

// Patch from src/conv.c - Adding size validation
// Source: https://github.com/zapping-vbi/zvbi/commit/ca1672134b3e2962cd392212c73f44f8f4cb489f

  * @returns
  * A pointer to the allocated buffer. You must free() the buffer
  * when it is no longer needed. The function returns @c NULL when
- * it runs out of memory, or when @a src is @c NULL.
+ * it runs out of memory, src_size is too large, or when @a src
+ * is @c NULL.
  *
  * @since 0.2.23
  */

// Patch from src/io-sim.c - Integer overflow check in buffer extension
// Source: https://github.com/zapping-vbi/zvbi/commit/ca1672134b3e2962cd392212c73f44f8f4cb489f

 		}
 
 		if (b->size >= b->capacity) {
-			if (!extend_buffer (b, b->capacity + 256))
+			unsigned int check_buffer_size = (b->capacity + 256);
+			if (b->capacity > check_buffer_size)
+				return FALSE;
+			if (!extend_buffer (b, check_buffer_size))
 				return FALSE;
 		}

Detection Methods for CVE-2025-2174

Indicators of Compromise

• Unexpected crashes or segmentation faults in applications utilizing libzvbi
• Memory corruption errors or heap-related warnings in system logs
• Abnormal memory allocation patterns in processes handling VBI data streams
• Applications processing VBI data exhibiting unexpected behavior or termination

Detection Strategies

• Monitor applications using libzvbi for abnormal memory allocation patterns and crashes
• Implement runtime detection using AddressSanitizer or similar memory safety tools during development and testing
• Deploy application-level monitoring to detect exploitation attempts targeting VBI processing functions
• Review system logs for segmentation faults or memory corruption indicators in processes utilizing libzvbi

Monitoring Recommendations

• Enable crash reporting and analysis for applications using the zvbi library
• Implement heap integrity monitoring in security-critical deployments
• Monitor for unusual input patterns in VBI data streams that may indicate exploitation attempts
• Track library versions across your infrastructure to identify vulnerable installations

How to Mitigate CVE-2025-2174

Immediate Actions Required

• Upgrade libzvbi to version 0.2.44 or later, which contains the security fix
• Audit systems and applications for vulnerable libzvbi installations
• If immediate upgrade is not possible, consider restricting network access to affected applications
• Review application architecture to limit exposure of VBI processing to untrusted input sources

Patch Information

The vulnerability has been addressed in libzvbi version 0.2.44. The fix is identified by commit hash ca1672134b3e2962cd392212c73f44f8f4cb489f. The patch adds proper integer overflow checks before buffer allocation operations in src/conv.c, src/io-sim.c, and src/search.c. The maintainer responded promptly and professionally to the security disclosure.

For patch details, refer to the GitHub Commit and the GitHub Security Advisory GHSA-g7cg-7gw9-v8cf.

Workarounds

• Restrict network access to applications utilizing vulnerable libzvbi versions
• Implement input validation at the application level before passing data to libzvbi functions
• Consider running affected applications in sandboxed environments to limit potential impact
• Deploy network-level filtering to limit exposure of VBI processing services to trusted sources only

# Upgrade libzvbi to patched version
# For systems using package managers:

# Debian/Ubuntu
sudo apt-get update && sudo apt-get install libzvbi-dev

# Fedora/RHEL
sudo dnf update zvbi

# Build from source with patched version
git clone https://github.com/zapping-vbi/zvbi.git
cd zvbi
git checkout v0.2.44
./configure && make && sudo make install