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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.1 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-34984: 0.26% estimated exploitation activity in the next 30 days; percentile 18.11 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

13 Apr 2026, 16:36 UTC

Last modified by the source

28 Apr 2026, 04:20 UTC

Source last checked

26 Oct 2026, 15:19 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-r2pg-r6h7-crf3

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# Patch Next advisory brief: CVE-2026-34984

Advisory: External Secrets Operator has DNS-based secret exfiltration via getHostByName in External Secrets v2 template engine
IDs: CVE-2026-34984, GHSA-r2pg-r6h7-crf3
Record: https://patchnext.com/advisories/cve-2026-34984 (revision 1, source checked 26 Oct 2026, 15:19 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/external-secrets/external-secrets 1.3.3-0.20260331202714-6800989bdc12. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/external-secrets/external-secrets: affected < 1.3.3-0.20260331202714-6800989bdc12; >= 2.0.0, <= 2.2.0; fixed in 1.3.3-0.20260331202714-6800989bdc12

## Suggested inspection (read-only)
- Go github.com/external-secrets/external-secrets: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/external-secrets/external-secrets.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-r2pg-r6h7-crf3 (GitHub-reviewed advisory GHSA-r2pg-r6h7-crf3 lists affected ranges: Go github.com/external-secrets/external-secrets >=0 =2.0.0 <=2.2.0)

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