Bug 2455868 (CVE-2026-28810)

Summary:	CVE-2026-28810 erlang/otp: Erlang/OTP kernel: DNS cache poisoning via predictable DNS transaction IDs
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	eglynn, jjoyce, jschluet, lhh, mburns, mgarciac
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in Erlang/OTP kernel. The built-in DNS resolver (inet_res) uses predictable 16-bit transaction IDs and lacks source port randomization. A remote attacker can exploit this by observing or predicting DNS query IDs, leading to DNS cache poisoning. This allows the attacker to redirect network traffic to malicious destinations.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2456134, 2456135
Bug Blocks:

Description OSIDB Bzimport 2026-04-07 09:01:28 UTC

Generation of Predictable Numbers or Identifiers vulnerability in Erlang/OTP kernel (inet_res, inet_db modules) allows DNS Cache Poisoning.

The built-in DNS resolver (inet_res) uses a sequential, process-global 16-bit transaction ID for UDP queries and does not implement source port randomization. Response validation relies almost entirely on this ID, making DNS cache poisoning practical for an attacker who can observe one query or predict the next ID. This conflicts with RFC 5452 recommendations for mitigating forged DNS answers.

inet_res is intended for use in trusted network environments and with trusted recursive resolvers. Earlier documentation did not clearly state this deployment assumption, which could lead users to deploy the resolver in environments where spoofed DNS responses are possible.

This vulnerability is associated with program files lib/kernel/src/inet_db.erl and lib/kernel/src/inet_res.erl.

This issue affects OTP from OTP 17.0 until OTP 28.4.2, 27.3.4.10 and 26.2.5.19 corresponding to kernel from 3.0 until 10.6.2, 10.2.7.4 and 9.2.4.11.