CVE-2026-53255 in Linux
Summary
by MITRE • 06/25/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: MGMT: validate advertising TLV before type checks
tlv_data_is_valid() reads each advertising data field length from data[i], then inspects data[i + 1] for managed EIR types before
checking that the current field still fits inside the supplied buffer.
A malformed field whose length byte is the last byte of the buffer can therefore make the parser read one byte past the advertising data.
KASAN reported the following when a malformed MGMT_OP_ADD_ADVERTISING request reached that path:
BUG: KASAN: vmalloc-out-of-bounds in tlv_data_is_valid() Read of size 1 Call trace: tlv_data_is_valid() add_advertising() hci_mgmt_cmd() hci_sock_sendmsg()
Move the existing element-length check before any type-octet inspection so each non-empty element is proven to contain its type byte before the parser looks at data[i + 1].
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Analysis
by VulDB Data Team • 06/25/2026
This vulnerability resides within the Linux kernel's Bluetooth management subsystem, specifically affecting the MGMT interface used for configuring Bluetooth advertising parameters. The flaw manifests in the tlv_data_is_valid() function which processes advertising data fields structured as Type-Length-Value (TLV) elements. When processing malformed advertising data, the function exhibits improper order of operations that creates a potential out-of-bounds memory access condition. The vulnerability stems from reading the length byte from data[i] and subsequently examining data[i + 1] for EIR type validation before confirming that the complete field fits within the supplied buffer boundaries. This sequence allows an attacker to craft malicious advertising data where a field's length byte occupies the final position of the buffer, causing the parser to access memory beyond the allocated bounds.
The technical implementation demonstrates a classic buffer overflow vulnerability pattern where input validation occurs in incorrect order. When the length byte equals the buffer size minus one, the parser attempts to read data[i + 1] which would point beyond the valid buffer range. This violates fundamental memory safety principles and creates an exploitable condition that KASAN detected during kernel runtime analysis. The specific call trace shows the vulnerability path through tlv_data_is_valid() function, then to add_advertising(), followed by hci_mgmt_cmd() and ultimately hci_sock_sendmsg(), indicating a complete flow from user input processing to kernel memory manipulation. This represents a type of heap-based buffer overflow that could potentially allow privilege escalation or system instability.
The operational impact of this vulnerability extends beyond simple memory corruption, as it affects the core Bluetooth management functionality within the Linux kernel. An attacker with access to send malformed MGMT_OP_ADD_ADVERTISING requests could trigger the out-of-bounds read condition, potentially leading to kernel crashes, information disclosure, or even arbitrary code execution depending on exploitation vector. The vulnerability directly relates to CWE-129 Input Validation and CWE-787 Out-of-bounds Read, both of which are classified as high-risk issues in cybersecurity standards. From an ATT&CK framework perspective, this vulnerability could enable initial access through Bluetooth management interfaces or facilitate privilege escalation once a system is compromised, particularly in environments where Bluetooth services run with elevated privileges.
The fix implements proper input validation ordering by moving the element-length check before type-octet inspection for each advertising data field. This ensures that any non-empty element must contain sufficient buffer space to accommodate both its length byte and type byte before proceeding with further validation. The solution aligns with defensive programming practices recommended in CERT Secure Coding standards, specifically addressing the principle of validating input boundaries before accessing structured data elements. By enforcing pre-validation checks, the patch prevents malformed data from causing memory access violations while maintaining compatibility with legitimate advertising data formats. This remediation approach follows industry best practices for handling TLV-encoded data structures and ensures that all buffer operations remain within allocated memory boundaries, effectively mitigating the potential for both immediate system instability and more sophisticated exploitation attempts targeting kernel memory corruption vulnerabilities.