CVE-2026-65421 in libiec61850
Summary
by MITRE • 07/31/2026
The MMS BER decoder contains a flaw in decoding fixed-width BER fields (boolean/integer): an attacker-supplied length value is not validated, causing a read past the end of a heap buffer. This leads to termination of the MMS service process and a denial-of-service condition.
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Analysis
by VulDB Data Team • 07/31/2026
The vulnerability described represents a critical buffer overflow condition within the MMS Basic Encoding Rules (BER) decoder implementation that fundamentally compromises the integrity of memory management during data processing operations. This flaw specifically targets the decoding of fixed-width BER fields including boolean and integer types, where the decoder fails to properly validate attacker-supplied length parameters before proceeding with memory access operations. The absence of proper input validation creates a scenario where maliciously crafted MMS messages can trigger unauthorized memory read operations beyond allocated heap buffer boundaries. The technical implementation demonstrates a classic out-of-bounds read vulnerability that operates at the protocol decoding layer, where the BER parser does not enforce bounds checking against the length field values provided by external inputs.
The operational impact of this vulnerability manifests as immediate service termination and complete denial-of-service conditions for affected MMS services. When an attacker crafts a malformed MMS message containing invalid length values within BER-encoded boolean or integer fields, the decoder attempts to read memory locations beyond the intended buffer allocation, resulting in segmentation faults or memory access violations that inevitably crash the MMS service process. This vulnerability directly aligns with CWE-129, which addresses insufficient validation of length fields, and represents a specific implementation weakness in the BER decoding logic that fails to adhere to proper input sanitization practices. The attack surface extends to any system utilizing the vulnerable MMS decoder component, particularly affecting mobile network infrastructure, messaging servers, and enterprise communication platforms that process MMS content.
From an adversarial perspective, this vulnerability enables attackers to execute remote denial-of-service attacks with minimal technical expertise required to craft malicious payloads. The attacker need only construct an MMS message with malformed BER length fields to trigger the buffer overflow condition, making this a highly attractive target for service disruption campaigns. The vulnerability's characteristics align with ATT&CK technique T1499.004, specifically targeting service availability through denial-of-service methods. The memory corruption resulting from heap buffer overreads can potentially be exploited further if additional vulnerabilities exist within the same codebase, though the immediate impact remains focused on process termination and service unavailability. Organizations should implement immediate patching strategies to address the validation gap in BER field decoding while establishing monitoring protocols to detect potential exploitation attempts targeting this specific vulnerability class.
The root cause analysis reveals that the decoder lacks proper bounds checking mechanisms before executing memory read operations on heap-allocated buffers, creating a fundamental security gap in the input processing pipeline. This flaw demonstrates poor defensive programming practices where external inputs are not adequately sanitized before being used in memory management operations. The vulnerability's exploitation requires no special privileges or advanced technical knowledge beyond basic message crafting capabilities, making it particularly dangerous for widespread deployment. Security teams should prioritize this vulnerability in their risk assessment matrices due to its potential for large-scale service disruption and the relative ease of exploitation. Mitigation strategies should include immediate code patches that enforce strict length validation, implement comprehensive input sanitization routines, and deploy intrusion detection systems capable of identifying malformed MMS traffic patterns associated with this specific vulnerability type.