CVE-2015-7974 in ntp
Summary
by MITRE
NTP 4.x before 4.2.8p6 and 4.3.x before 4.3.90 do not verify peer associations of symmetric keys when authenticating packets, which might allow remote attackers to conduct impersonation attacks via an arbitrary trusted key, aka a "skeleton key."
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 07/06/2022
The vulnerability identified as CVE-2015-7974 affects the Network Time Protocol implementation in versions prior to 4.2.8p6 and 4.3.90, presenting a critical security flaw in how NTP handles symmetric key authentication. This issue resides in the peer association verification process during packet authentication, creating a pathway for remote attackers to exploit the system through what is termed a "skeleton key" attack vector. The flaw specifically targets the authentication mechanism used to verify the legitimacy of time synchronization communications between NTP peers.
The technical implementation of this vulnerability stems from insufficient validation of peer associations when symmetric keys are used for authentication purposes. In standard NTP operations, symmetric key authentication relies on both peers maintaining synchronized key material to validate packet authenticity. However, the flaw allows an attacker to bypass this verification step, enabling them to authenticate packets using any trusted key from the configuration rather than requiring proper peer association. This creates a scenario where attackers can impersonate legitimate NTP peers and inject malicious time synchronization data into the network.
From an operational perspective, this vulnerability poses significant risks to network infrastructure relying on NTP for time synchronization services. Attackers exploiting this weakness can manipulate time stamps across networked systems, potentially disrupting critical services that depend on accurate timekeeping such as financial transactions, security logging, and distributed system coordination. The impact extends beyond simple time manipulation to include potential system compromise through time-based attacks, as accurate time synchronization is fundamental to many security protocols and cryptographic operations.
The vulnerability aligns with CWE-310, which addresses cryptographic weaknesses in authentication mechanisms, specifically targeting improper verification of cryptographic parameters. It also maps to ATT&CK technique T1562.001, which involves modifying system time, and T1071.004, covering application layer protocol usage for command and control communications. Organizations should implement immediate mitigations including upgrading to NTP versions 4.2.8p6 or 4.3.90, disabling unnecessary symmetric key authentication when not required, and implementing network segmentation to limit exposure. Additionally, monitoring for anomalous time synchronization behavior and implementing proper key management practices can help detect and prevent exploitation attempts. The fix addresses the root cause by enforcing proper peer association validation during symmetric key authentication, ensuring that only legitimate peer associations can be used for packet verification.