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🛡️ CVE-2026-45673 — netty

🟡 CVSS 6.8 — Medium ✅ No Known Exploit CWE-330 NVD
6.8
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality none, integrity high, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Changed — a successful attack reaches components beyond the vulnerable one.
  • Confidentiality impact: None.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: None.

Weakness class

CVE-2026-45673 is classified as CWE-330: Use of Insufficiently Random Values. Values that must be unpredictable are generated in a way an attacker can guess or reproduce.

Affected software

CVE-2026-45673 is recorded against 2 packages.

  • io.netty:netty-resolver-dns (fixed in 4.1.135.Final)
  • netty (from 4.2.0 up to 4.2.15)

Timeline and source

Published on 8 June 2026 and last revised on 12 June 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Package)
github.com (Web)
github.com (Web)

Other advisories for this package

io.netty:netty-resolver-dns has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-330: Use of Insufficiently Random Values) in other software:

CVE-2026-45673 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Medium
CVSS Score 6.8
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N
CWE CWE-330
Public Exploit ✅ No
Source NVD
Published 2026-06-08
Updated 2026-08-20
Modified 2026-06-12
Fix URL N/A

Affected Packages

Software From version Fixed in
io.netty:netty-resolver-dns — 4.1.135.Final
netty 4.2.0 4.2.15

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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