CVE-2026-1005 Overview
An integer underflow vulnerability exists in the wolfSSL packet sniffer component in versions 5.8.4 and earlier. The flaw allows an attacker to cause a buffer overflow in the AEAD decryption path by injecting a TLS record shorter than the explicit IV plus authentication tag into traffic inspected by ssl_DecodePacket. When processing these malformed records, the underflow wraps a 16-bit length value to a large value that is subsequently passed to AEAD decryption routines, causing heap buffer overflow and a crash.
Critical Impact
An unauthenticated attacker can trigger this vulnerability remotely via malformed TLS Application Data records, potentially causing denial of service conditions in systems using the wolfSSL packet sniffer for traffic inspection.
Affected Products
- wolfSSL packet sniffer versions <= 5.8.4
Discovery Timeline
- March 19, 2026 - CVE CVE-2026-1005 published to NVD
- March 19, 2026 - Last updated in NVD database
Technical Details for CVE-2026-1005
Vulnerability Analysis
This vulnerability is classified as CWE-191 (Integer Underflow). The integer underflow occurs in the wolfSSL packet sniffer when processing TLS Application Data records. When a TLS record with a length shorter than the combined size of the explicit IV and authentication tag is received, the length calculation results in an underflow condition. Since the length is stored as a 16-bit unsigned integer, this underflow causes the value to wrap around to a large positive number.
The oversized length value is then passed to the AEAD (Authenticated Encryption with Associated Data) decryption routines, which attempt to process a much larger buffer than actually exists. This leads to a heap buffer overflow, resulting in memory corruption and application crash.
Root Cause
The root cause is insufficient validation of the TLS record length before performing arithmetic operations in the ssl_DecodePacket function. The code does not verify that the record length is at least as large as the combined size of the explicit IV and authentication tag before subtracting these values. When a malicious record is received with a smaller length, the subtraction underflows the 16-bit unsigned integer.
Attack Vector
An unauthenticated remote attacker can exploit this vulnerability by injecting specially crafted TLS Application Data records into network traffic being inspected by systems using the vulnerable wolfSSL packet sniffer. The attack requires network access to send malformed TLS records that will be processed by the packet sniffer component.
The attacker crafts a TLS record where the payload length is smaller than the expected overhead (explicit IV + authentication tag). When the packet sniffer attempts to calculate the actual data length by subtracting the overhead from the record length, the result underflows, producing a very large value that triggers a heap buffer overflow during AEAD decryption.
Detection Methods for CVE-2026-1005
Indicators of Compromise
- Unexpected crashes or service restarts in applications using the wolfSSL packet sniffer
- Memory corruption errors or segmentation faults in processes performing TLS traffic inspection
- Presence of malformed TLS Application Data records with unusually short payload lengths in network captures
Detection Strategies
- Monitor for application crashes in services utilizing wolfSSL packet sniffer functionality
- Implement network-based detection rules to identify TLS records with payload lengths shorter than minimum expected values
- Review system logs for heap corruption or buffer overflow-related errors in wolfSSL-dependent applications
Monitoring Recommendations
- Enable verbose logging for wolfSSL components to capture detailed error information
- Set up alerting for abnormal process terminations in systems running wolfSSL packet sniffer
- Monitor network traffic for anomalous TLS record patterns that could indicate exploitation attempts
How to Mitigate CVE-2026-1005
Immediate Actions Required
- Upgrade wolfSSL to a version newer than 5.8.4 that includes the fix for this vulnerability
- If immediate patching is not possible, consider disabling or restricting access to packet sniffer functionality
- Monitor affected systems for signs of exploitation or abnormal behavior
Patch Information
The fix for this vulnerability is available via the GitHub Pull Request for wolfSSL. The patch adds proper validation of TLS record lengths before performing arithmetic operations, ensuring that underflow conditions cannot occur when processing malformed records.
Workarounds
- Disable the wolfSSL packet sniffer functionality if not strictly required until patching is possible
- Implement network filtering to drop TLS records with suspiciously small payload lengths before they reach vulnerable systems
- Isolate systems using the wolfSSL packet sniffer from untrusted network traffic where feasible
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
