SSRF (Server-Side Request Forgery) in io.kestra:core (CVE-2026-73247)
Summary
SSRF in io.kestra:core (CVE-2026-73247). Confidential information can be exposed externally. Exploitable via TenantValidationFilter.java. Mitigation: upgrade to 2.0.0 or later.
Original description
The description as published by the source.
Summary
The Pebble template engine's http() function in Kestra OSS accepts user-controlled URLs without any validation, allowing Server-Side Request Forgery (SSRF) attacks. An unauthenticated attacker can import a malicious Flow YAML and execute it to access internal services, cloud metadata endpoints (AWS 169.254.169.254), or localhost services. The vulnerability affects all Kestra OSS deployments with default configuration.
Details
The root cause is in core/src/main/java/io/kestra/core/runners/pebble/functions/HttpFunction.java (lines 77-106):
- No URL validation: User input is passed directly to
URI.create()with no checks for private IPs, internal hosts, or restricted schemes - No IP filtering: Missing checks for 10.0.0.0/8, 192.168.0.0/16, 169.254.169.254, 127.0.0.1
- No scheme restriction:
file://,gopher://schemes are not blocked - No authentication required:
TenantValidationFilter.javaonly checks tenant == "main" — no authentication - Unconditional registration:
HttpFunctionis registered without any feature flags inExtension.java:180
PoC
Prerequisites:
docker run -d --name kestra-ssrf -p 8080:8080 kestra/kestra:latest server local
sleep 30
Step 1: Create malicious Flow YAML
cat > /tmp/ssrf_poc.yaml << 'YAML'
id: ssrf_metadata
namespace: company.team
tasks:
- id: exfiltrate
type: io.kestra.plugin.core.log.Log
message: |
{{ http(uri='http://169.254.169.254/latest/met…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-73247 has been found in io.kestra:core.
Attackers can target a specific entry point like TenantValidationFilter.java over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.6/10.
What to do: upgrade io.kestra:core to 2.0.0 or later.
If unsure, ask your IT team or search "io.kestra:core CVE-2026-73247" on the vendor's site.
CVE-2026-73247 (io.kestra:core) — CWE-918 / CVSS v3 8.6
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: TenantValidationFilter.java / HttpFunction
Patched: 2.0.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
SSRF (CWE-918) exists in io.kestra:core. Attackers reach the vulnerable code path via TenantValidationFilter.java without authentication.
Check the vendor advisory for the affected versions of io.kestra:core. Attack surface: TenantValidationFilter.java / HttpFunction.
Severity: High (CVSS 8.6/10). Confidential information can be exposed externally.
Update to 2.0.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで io.kestra:core を使っているサービスとバージョンを洗い出す。
-
2Apply patch patch
Upgrade io.kestra:core to 2.0.0ステージング環境で 2.0.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- web github.com
- web nvd.nist.gov
- web github.com