# CVE-2026-28810: Predictable DNS Transaction IDs Enable Cache Poisoning in Built-in Resolver

Status: published. Published: 2026-04-07. Updated: 2026-11-11.

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 before OTP 26.2.5.19, OTP 27.3.4.10, and OTP 28.4.2, corresponding to kernel from 3.0 before 9.2.4.11, 10.2.7.4, and 10.6.2.

## Remediation

- workaround: Install the Erlang nodes in a trusted network shielded from DNS reply spoofing by firewalls, and configure the inet_res resolver to only talk to trusted recursive name servers within that network. (source: CNA: EEF)
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/erlang/otp/commit/b057a9d995017b1be50d6dc02edd52382f3231b8
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/erlang/otp/commit/dd15e8eb03548c5e55e9915f0e91389ec6bad9fd
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/erlang/otp/commit/36f23c9d2cc54afe83671dd7343596d7972839a5

## Affected products and versions

- Erlang / OTP (otp): ≥ 17.0; < * (affected, otp); unaffected at 26.2.5.19; unaffected at 27.3.4.10; unaffected at 28.4.2. Source: CNA: EEF
- Erlang / OTP (kernel): ≥ 3.0; < * (affected, otp); unaffected at 9.2.4.11; unaffected at 10.2.7.4; unaffected at 10.6.2. Source: CNA: EEF
- Erlang / OTP (erlang/otp): ≥ 07b8f441ca711f9812fad9e9115bab3c3aa92f79; < b057a9d995017b1be50d6dc02edd52382f3231b8 (affected, git). Source: CNA: EEF

## Severity and prioritization

- CVSS 4.0: 6.3 (medium); CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N; source: CNA: EEF

- CISA KEV: No listing in collected sources

- EPSS: 0.27% as of 2026-11-10; percentile 19.97%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-340

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/erlang/otp/security/advisories/GHSA-v884-5jg5-whj8 (CNA: EEF; vendor-advisory, related)

- https://cna.erlef.org/cves/CVE-2026-28810.html (CNA: EEF; related)

- https://osv.dev/vulnerability/EEF-CVE-2026-28810 (CNA: EEF; related)

- https://www.erlang.org/doc/system/versions.html#order-of-versions (CNA: EEF; x_version-scheme)

- https://github.com/erlang/otp/commit/07b8f441ca711f9812fad9e9115bab3c3aa92f79 (CNA: EEF; related)

- https://github.com/erlang/otp/commit/b057a9d995017b1be50d6dc02edd52382f3231b8 (CNA: EEF; patch)

- https://github.com/erlang/otp/commit/dd15e8eb03548c5e55e9915f0e91389ec6bad9fd (CNA: EEF; patch)

- https://github.com/erlang/otp/commit/36f23c9d2cc54afe83671dd7343596d7972839a5 (CNA: EEF; patch)

## Provenance

- CNA: EEF: https://www.cve.org/CVERecord?id=CVE-2026-28810; retrieved 2026-11-11; source updated 2026-11-11

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-28810; retrieved 2026-11-11; source updated Not reported

Revision: 1eec7fb5c27b188c3ad694c414425ffa69561b290acfce9fbd5a081b4b33e189

Canonical: https://y2.dev/cve/CVE-2026-28810

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