CVE-2026-13077 in Server
Summary
by MITRE • 07/22/2026
A missing bounds check in the BSON CodeWScope element accessors allows an attacker to trigger an out-of-bounds heap read via a crafted aggregation pipeline. The vulnerability can be exploited by an authenticated user by generating a malformed BSONColumn data containing a CodeWScope element, bypassing wire-level BSON validation. When the forged element is decompressed, the unchecked size value is used in pointer arithmetic, causing either a server crash or disclosure of adjacent heap memory contents.
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Analysis
by VulDB Data Team • 07/23/2026
This vulnerability represents a critical heap-based buffer overflow condition within BSON (Binary JSON) processing libraries that affects database systems utilizing aggregation pipelines. The flaw exists specifically in the CodeWScope element accessors where proper bounds checking has been omitted during deserialization operations. The vulnerability manifests when an authenticated user crafts malicious BSON data containing a CodeWScope element that bypasses initial wire-level validation mechanisms, allowing the malformed data to proceed through the decompression and parsing stages of the database engine.
The technical implementation of this vulnerability stems from improper input validation during BSON document processing where size fields within the CodeWScope element are not adequately verified before being used in pointer arithmetic operations. When the maliciously constructed element undergoes decompression, the unchecked size value is directly employed in memory calculations without proper range verification or boundary checks. This fundamental flaw in the validation logic creates an exploitable condition where attacker-controlled data can manipulate heap memory pointers to access regions beyond the intended buffer boundaries.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to include potential information disclosure and system instability. An authenticated attacker with sufficient privileges can leverage this weakness to either cause a server crash through memory corruption or extract sensitive heap contents that may contain database credentials, user information, or other confidential data. The exploitation requires the attacker to have valid authentication credentials for the database system, making it particularly dangerous in environments where privileged accounts exist or where privilege escalation has occurred.
From a cybersecurity framework perspective, this vulnerability maps directly to CWE-129 and CWE-787 within the Common Weakness Enumeration catalog, specifically addressing issues related to insufficient bounds checking and out-of-bounds read conditions. The attack vector aligns with ATT&CK technique T1059.006 for Command and Scripting Interpreter and T1499.004 for Network Denial of Service, potentially enabling both service disruption and information gathering operations. The vulnerability's exploitation path involves crafting malicious data within the aggregation pipeline framework, which represents a sophisticated attack approach that requires understanding of the database's internal data structures and BSON parsing mechanisms.
Effective mitigation strategies should focus on implementing comprehensive input validation at multiple layers including wire-level checks, decompression boundary verification, and runtime memory protection mechanisms. Database administrators should ensure all systems are updated with patched versions that include proper bounds checking for BSON element size fields. Additionally, monitoring systems should be configured to detect unusual aggregation pipeline operations and malformed BSON data patterns that could indicate exploitation attempts. Network segmentation and principle of least privilege access controls can help limit the potential impact even if exploitation occurs, while regular security audits should verify that all BSON parsing components include adequate validation routines to prevent similar vulnerabilities from emerging in future releases.