External Secrets Operator has DNS-based secret exfiltration via getHostByName in External Secrets v2 template engine

中 6.5CVE-2026-34984 · GHSA-r2pg-r6h7-crf3 · GO-2026-5602 · 14/04/2026 公開 · 17/06/2026 更新

要点

CVE-2026-34984 は github.com/external-secrets/external-secrets, external secrets operator (external-secrets) に影響する深刻度「中」 (CVSS 6.5) の脆弱性です。
今後30日間に悪用される確率（EPSS）：0.26%（全脆弱性の 18.1% より高い）。
対処：1.3.3-0.20260331202714-6800989bdc12, 2.3.0 以降に更新してください。

パッケージ	影響を受けるバージョン	修正済みバージョン
github.com/external-secrets/external-secrets Go	`≥ 2.0.0, ≤ 2.2.0< 1.3.3-0.20260331202714-6800989bdc12`	`1.3.3-0.20260331202714-6800989bdc12`
external secrets operator external-secrets	`< 2.3.0`	`2.3.0`

概要

Summary

The v2 template engine in runtime/template/v2/template.go imports Sprig’s TxtFuncMap() and removes env and expandenv, but leaves getHostByName available to user-controlled templates. Because ESO executes templates inside the controller process, an attacker who can create or update templated ExternalSecret resources can trigger controller-side DNS lookups using secret-derived values, creating a DNS exfiltration primitive.

Impact

This is a confidentiality issue. In environments where untrusted or lower-trust users can author templated ExternalSecret resources and the controller can perform DNS resolution, fetched secret material can be exfiltrated through DNS without requiring direct outbound access from the attacker’s workload.

NVD の説明

External Secrets Operator reads information from a third-party service and automatically injects the values as Kubernetes Secrets. Versions 2.2.0 and below contain a vulnerability in runtime/template/v2/template.go where the v2 template engine removes env and expandenv from Sprig's TxtFuncMap() but leaves the getHostByName function accessible to user-controlled templates. Since ESO executes templates within the controller process, an attacker who can create or update templated ExternalSecret resources can invoke controller-side DNS lookups using secret-derived values. This creates a DNS exfiltration primitive, allowing fetched secret material to be leaked via DNS queries without requiring direct outbound network access from the attacker's workload. The impact is a confidentiality issue, particularly in environments where untrusted or lower-trust users can author templated ExternalSecret resources and the controller has DNS resolution capability. This issue has been fixed in version 2.3.0.