Netty DNS Resolver PRNG Flaw Enables Cache Poisoning (pre4.1.135/4.2.15)
CVE-2026-45673 Published on June 12, 2026
Netty: DNS Cache Poisoning due to Predictable PRNG and Default Static Source Port
Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, Netty's DNS resolver uses a predictable PRNG for generating DNS transaction IDs and defaults to a static UDP source port. This combination reduces the entropy of DNS queries, enabling DNS Cache Poisoning (Kaminsky attack). Versions 4.1.135.Final and 4.2.15.Final patch the issue.
Vulnerability Analysis
CVE-2026-45673 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, a high impact on integrity, and no impact on availability.
Weakness Types
Use of Insufficiently Random Values
The software uses insufficiently random numbers or values in a security context that depends on unpredictable numbers. When software generates predictable values in a context requiring unpredictability, it may be possible for an attacker to guess the next value that will be generated, and use this guess to impersonate another user or access sensitive information.
Generation of Predictable Numbers or Identifiers
The product uses a scheme that generates numbers or identifiers that are more predictable than required.
Products Associated with CVE-2026-45673
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Affected Versions
netty:- Version >= 4.2.0.Final, < 4.2.15.Final is affected.
- Version < 4.1.135.Final is affected.