CVE-2026-121507 in µD3TN
Summary
by MITRE • 11/03/2026
Double Free in µD3TN BPv6 Fragmenter Block Duplication allows Unauthenticated Remote Attacker to Cause DoS on Allocation Failure
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified as a double free error within the µD3TN BPv6 fragmenter block duplication mechanism represents a critical memory management flaw that can be exploited by unauthenticated remote attackers. This specific defect occurs during the processing of IPv6 fragments in the context of Delay-Tolerant Networking (DTN) Bundle Protocol version 6 implementations. The core issue lies in how the system handles memory allocation failures when attempting to duplicate fragment blocks for reassembly or forwarding purposes. Under normal operational conditions, the software allocates new memory buffers to hold duplicated data structures required for processing incoming network packets. However, if the underlying operating system fails to provide sufficient memory resources due to exhaustion or fragmentation, the application logic incorrectly proceeds with cleanup routines that assume successful allocation had occurred.
This logical error leads directly to a double free condition, where the same block of dynamically allocated memory is released more than once by the program's execution flow. In C-based systems and many other low-level programming environments, freeing already freed memory corrupts the heap metadata structures managed by the allocator. This corruption can manifest in various ways depending on the specific runtime environment and compiler optimizations employed. The most immediate and observable consequence of this flaw is a denial of service condition. When the double free operation triggers an assertion failure or causes undefined behavior within the process, the affected application typically crashes abruptly. Since this vulnerability resides in a network-facing component responsible for handling incoming traffic, it can be triggered remotely without requiring any form of authentication from the attacker.
The operational impact of this denial of service is significant because DTN systems are often deployed in environments where reliability and continuous operation are paramount, such as satellite communications, deep space networks, or tactical military communications with intermittent connectivity links. An unauthenticated remote attacker can craft specific IPv6 fragment sequences that force the system into a state where memory allocation fails during block duplication. By repeatedly sending these crafted packets, an attacker can induce repeated crashes of the DTN endpoint software, effectively rendering the node unavailable for legitimate traffic processing. This disruption compromises the availability aspect of the CIA triad and can lead to broader network instability if multiple nodes in the mesh are targeted simultaneously.
From a classification perspective, this vulnerability aligns with CWE-415 Double Free, which describes situations where memory is freed twice leading to heap corruption or application crashes. It also relates closely to CWE-789 Memory Allocation Race Conditions and CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization if the issue involves race conditions during allocation failure handling. In terms of offensive security frameworks, this vulnerability facilitates Denial of Service attacks categorized under MITRE ATT&CK technique T1499 Endpoint Denial of Service. Attackers can leverage this flaw to degrade service quality or completely halt operations on vulnerable DTN nodes without needing prior access credentials.
Mitigation strategies for this vulnerability require both immediate patching and long-term architectural improvements. The primary remediation involves updating the µD3TN software stack to a version that includes proper error handling logic within the fragmenter block duplication routine. Developers must ensure that memory allocation functions are checked for null returns before any subsequent operations, including deallocation routines, are executed. If an allocation fails, the program should abort the current operation and clean up only those resources that were successfully allocated during that specific transaction sequence. Additionally implementing robust input validation to limit the rate of incoming IPv6 fragments can help mitigate resource exhaustion attacks that trigger the underlying memory pressure leading to this flaw.
Long-term resilience against such vulnerabilities involves adopting secure coding practices that emphasize defensive programming techniques. This includes using static analysis tools and dynamic fuzzing during development phases to identify potential double free scenarios before deployment. Furthermore, employing heap protection mechanisms provided by modern operating systems, such as Address Space Layout Randomization (ASLR) and Heap Canaries, can help detect or prevent exploitation attempts even if the underlying code flaw persists temporarily until a full patch is applied. Regular security audits focusing on memory management logic in network processing modules are essential to maintain the integrity of critical infrastructure relying on DTN technologies.