CVE-2006-6013 in FreeBSD
Summary
by MITRE
Integer signedness error in the fw_ioctl (FW_IOCTL) function in the FireWire (IEEE-1394) drivers (dev/firewire/fwdev.c) in various BSD kernels, including DragonFlyBSD, FreeBSD 5.5, MidnightBSD 0.1-CURRENT before 20061115, NetBSD-current before 20061116, NetBSD-4 before 20061203, and TrustedBSD, allows local users to read arbitrary memory contents via certain negative values of crom_buf->len in an FW_GCROM command. NOTE: this issue has been labeled as an integer overflow, but it is more like an integer signedness error.
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Analysis
by VulDB Data Team • 04/28/2026
The vulnerability described in CVE-2006-6013 represents a critical integer signedness error within the FireWire IEEE-1394 driver implementations across multiple BSD operating systems. This flaw exists in the fw_ioctl function within the dev/firewire/fwdev.c file, where the system fails to properly validate the signedness of integer values during device communication operations. The vulnerability specifically manifests when processing FW_GCROM commands, where the crom_buf->len parameter contains negative values that are not properly handled by the kernel driver, creating a potential pathway for unauthorized memory access.
The technical implementation of this vulnerability stems from the improper handling of signed integer values in kernel space operations. When a FireWire device sends an FW_GCROM command with a negative value in the crom_buf->len field, the kernel's fw_ioctl function does not validate that this value remains within expected positive bounds. This oversight allows an attacker to manipulate the length parameter to negative values, which then gets interpreted as a valid memory access request. The underlying issue is classified as a CWE-191 Integer Underflow (Wrap or Wraparound) since the negative value causes the integer to wrap around to a large positive value, potentially enabling access to memory regions outside the intended buffer boundaries.
The operational impact of this vulnerability is significant for systems running affected BSD variants, as it provides local users with the ability to read arbitrary memory contents from the kernel space. This capability can be leveraged to extract sensitive information including kernel memory structures, cryptographic keys, or other confidential data that may be stored in accessible memory regions. The vulnerability does not require network access or specific privileges beyond local user access, making it particularly dangerous in multi-user environments where an unprivileged user could potentially exploit this weakness to gain information that could be used in further attacks.
This vulnerability aligns with ATT&CK technique T1005 - Data from Local System, where adversaries can extract data from the compromised system. The integer signedness error creates a direct pathway for memory disclosure attacks that could be combined with other exploitation techniques to escalate privileges or discover additional system information. The affected systems include several major BSD implementations including DragonFlyBSD, FreeBSD 5.5, MidnightBSD 0.1-CURRENT, NetBSD-current, NetBSD-4, and TrustedBSD, indicating a widespread impact across the BSD ecosystem. The vulnerability's classification as integer signedness error rather than integer overflow reflects the specific nature of the flaw where signedness handling is inadequate rather than pure arithmetic overflow.
Mitigation strategies for this vulnerability require immediate patching of all affected BSD kernel versions, as the flaw exists in the core device driver functionality. System administrators should ensure that all BSD systems are updated to versions containing the appropriate fixes for the fw_ioctl function's handling of the crom_buf->len parameter. Additionally, implementing proper input validation and bounds checking in kernel space operations can prevent similar issues in the future. The fix typically involves adding explicit validation to ensure that length parameters remain within expected positive ranges before being used in memory operations, preventing the wraparound behavior that enables arbitrary memory reads. Organizations should also consider implementing monitoring for unusual FireWire device activity and network traffic patterns that might indicate exploitation attempts.