CVE-2014-5355 in Kerberos
Summary
by MITRE
MIT Kerberos 5 (aka krb5) through 1.13.1 incorrectly expects that a krb5_read_message data field is represented as a string ending with a '\0' character, which allows remote attackers to (1) cause a denial of service (NULL pointer dereference) via a zero-byte version string or (2) cause a denial of service (out-of-bounds read) by omitting the '\0' character, related to appl/user_user/server.c and lib/krb5/krb/recvauth.c.
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Analysis
by VulDB Data Team • 03/10/2022
The vulnerability described in CVE-2014-5355 affects MIT Kerberos 5 versions through 1.13.1 and represents a critical input validation flaw that stems from improper handling of string termination within the Kerberos authentication protocol implementation. This issue manifests in the krb5_read_message function where the code assumes that all data fields are properly null-terminated strings, creating a dangerous assumption that can be exploited by remote attackers to manipulate the authentication process. The flaw exists in core Kerberos components including appl/user_user/server.c and lib/krb5/krb/recvauth.c, which are fundamental to the Kerberos authentication workflow and server communication protocols.
The technical exploitation of this vulnerability occurs through two distinct attack vectors that leverage the improper string handling logic. The first vector involves sending a zero-byte version string which triggers a NULL pointer dereference during message processing, effectively causing a denial of service condition that crashes the Kerberos server or client application. The second vector exploits the absence of the expected null termination character, leading to out-of-bounds memory reads that can cause unpredictable behavior and potentially allow for information disclosure or further exploitation. Both attack scenarios stem from the same underlying flaw where the code fails to properly validate input data before processing, violating fundamental security principles of input sanitization and bounds checking.
From an operational impact perspective, this vulnerability poses significant risks to organizations relying on Kerberos authentication systems as it can be exploited remotely without authentication, making it particularly dangerous for network services that depend on Kerberos for secure authentication. The denial of service conditions can disrupt critical services, while the out-of-bounds read may potentially expose sensitive memory contents or allow attackers to gain additional insights into the system's internal state. Given that Kerberos is widely used in enterprise environments for single sign-on, secure communication, and identity management, a successful exploitation could compromise the availability and integrity of authentication services across affected networks.
The vulnerability aligns with CWE-129, which addresses improper validation of array indices and buffer overflows, and CWE-707, which covers improper neutralization of special elements used in a command. From an ATT&CK framework perspective, this vulnerability maps to T1190 - Exploit Public-Facing Application and T1499 - Endpoint Denial of Service, representing both network-level exploitation capabilities and service disruption potential. The attack requires minimal privileges and can be executed remotely, making it particularly attractive to threat actors seeking to disrupt authentication services or gain a foothold in enterprise environments. Organizations should prioritize patching this vulnerability as it represents a fundamental flaw in the core authentication infrastructure that can be exploited to undermine the security posture of entire network domains relying on Kerberos for secure authentication.
Mitigation strategies should include immediate deployment of patches from MIT Kerberos maintainers to address the string handling inconsistencies in the affected code modules. Network segmentation and monitoring of Kerberos traffic can help detect potential exploitation attempts, while implementing proper input validation at multiple layers of the authentication stack can provide additional defense-in-depth. Security teams should also consider implementing intrusion detection systems configured to identify malformed Kerberos messages that may indicate exploitation attempts, and regular security assessments of Kerberos implementations should be conducted to identify similar input validation weaknesses in related components.