Vulnerability
Netty: DNS Cache Poisoning due to Predictable PRNG and Default Static Source Port
### Summary 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). ### Details Two factors contribute to this vulnerability in io.netty.resolver.dns: - Predictable Query IDs: `DnsQueryIdSpace` manages 16-bit transaction IDs in buckets of 16,384 IDs. It initializes only the first bucket. When an ID is returned, it is pushed back into the bucket at a random index generated by java.util.concurrent.ThreadLocalRandom: ```java Random random = ThreadLocalRandom.current(); int insertionPosition = random.nextInt(count + 1); ``` Because ThreadLocalRandom is a predictable LCG and the resolver operates within a single bucket, the sequence of IDs is predictable once the PRNG state is mathematically recovered. - Default Static Source Port: `DnsNameResolverBuilder` defaults to a `channelStrategy` of `ChannelPerResolver`. This binds the DatagramChannel once, resulting in a static source port for all subsequent queries. Combined, a static source port and predictable transaction IDs reduces the entropy required to secure DNS resolution against spoofing. ### Impact DNS Cache Poisoning. Downstream applications using the default Netty DNS resolver may connect to malicious IPs, leading to traffic interception or MitM attacks.
No CVSS base score from NVD or GHSA yet. NVD typically scores within 24–72 hours of publication; GHSA usually within a day for OSS-flagged CVEs. Last record update .
For interim severity, fall back on KEV / EXPLOIT signals and the EPSS percentile (lower panel). Re-check this CVE after one cron tick — the score lands automatically when the source publishes.
Low exploitation likelihood — defer if no other signals fire.
No VEX statements published for CVE-2026-45673. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.
No exploitation, limited impact or prevalence