CVE-2026-58216 in Red Hat
Summary
by MITRE • 07/30/2026
An out-of-bounds read flaw was found in Samba's Kerberos Key Distribution Center's (KDC) password change (kpasswd) service. When processing malformed ASN.1-encoded Kerberos password change request, Samba server miscalculates the structure size and attempts to read up to six bytes beyond the end of the allocated buffer. While this out-of-bounds read typically results in a harmless decryption failure, if the read hits unmapped memory, it causes the KDC process to crash. An authenticated attacker can send a specially crafted kpasswd request containing malformed ASN.1 data to trigger the out-of-bounds read, which may cause the KDC process to terminate, resulting in a denial of service.
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Analysis
by VulDB Data Team • 07/30/2026
This vulnerability resides within Samba's Kerberos Key Distribution Center implementation where the kpasswd service fails to properly validate ASN.1-encoded packet structures during password change operations. The flaw manifests as an out-of-bounds read condition that occurs when processing maliciously crafted Kerberos requests, specifically targeting the buffer management logic responsible for parsing password change packets. According to CWE-129, this represents an insufficient input validation issue where the application fails to properly check array bounds before accessing memory regions. The vulnerability stems from improper calculation of structure sizes during ASN.1 decoding, causing the application to attempt memory access beyond allocated buffer boundaries.
The technical execution of this vulnerability requires an authenticated attacker who can submit specially crafted kpasswd requests containing malformed ASN.1 data structures. When the KDC processes these requests, it incorrectly calculates the size of expected data structures and proceeds to read up to six bytes beyond valid buffer limits. This out-of-bounds memory access typically results in decryption failures that do not immediately compromise system integrity but can be exploited for denial of service attacks. The vulnerability specifically impacts the KDC process which serves as the central authentication authority for Kerberos ticket management, making it a critical component for maintaining network security infrastructure.
From an operational standpoint, this vulnerability creates significant risk for organizations relying on Samba-based Kerberos implementations, particularly those using Samba as a domain controller or integrated authentication service. The potential for denial of service attacks against the KDC process means that legitimate authentication requests may fail, disrupting access to network resources and services that depend on Kerberos authentication. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1499 for endpoint denial of service, where adversaries target critical system processes to disrupt operations. The impact extends beyond simple service interruption as it affects the core authentication infrastructure that many enterprise systems depend upon.
Organizations should implement immediate mitigations including patching Samba installations to address the buffer overflow vulnerability in the KDC password change service. Network segmentation and access controls can help limit exposure by restricting which systems can submit kpasswd requests, though this approach provides only partial protection. Monitoring for unusual authentication patterns or repeated failed password change attempts may help detect exploitation attempts. The vulnerability highlights the importance of proper input validation and bounds checking in cryptographic implementations, particularly in authentication services where malformed data processing can lead to system instability. Organizations should also consider implementing additional authentication monitoring tools that can detect anomalous behavior patterns consistent with attempted exploitation of similar buffer overflow conditions.
The root cause analysis reveals that this issue stems from inadequate memory management during ASN.1 parsing operations within the Kerberos implementation, specifically in how the application calculates and validates structure sizes before accessing memory regions. This type of vulnerability represents a classic example of insufficient bound checking that can be exploited through carefully crafted input data. The combination of authentication requirements and the potential for process termination makes this particularly dangerous as it allows attackers with valid credentials to disrupt critical infrastructure services. Security teams should prioritize patching this vulnerability while also reviewing other cryptographic implementations for similar buffer management flaws.
This vulnerability demonstrates the critical importance of proper input validation in security-sensitive applications, particularly those handling authentication protocols where malformed data can lead to system instability or denial of service conditions. The flaw's impact extends beyond immediate service disruption to potentially undermining broader network security infrastructure that depends on Kerberos authentication services. Organizations implementing Samba-based solutions should conduct comprehensive vulnerability assessments to identify similar issues in other components and ensure robust memory management practices are employed throughout their authentication infrastructure. The remediation approach must include not only patching the specific vulnerability but also establishing monitoring procedures to detect potential exploitation attempts against similar buffer overflow conditions in related services.
The technical nature of this vulnerability aligns with common weaknesses identified in cryptographic protocol implementations where insufficient validation of external inputs leads to memory corruption issues. This particular flaw represents a convergence of improper bounds checking and malformed data handling that requires careful attention during security code reviews and penetration testing activities. The authentication requirement for exploitation provides some protection against unauthenticated attacks but does not eliminate the threat entirely, as compromised accounts can still be leveraged for denial of service operations against critical infrastructure components.