CVE-2026-20253 — SPLUNK
CRITICALCVE-2026-20253 is a critical-severity (CVSS 9.8) Missing Authentication vulnerability in splunk splunk. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-06-18) — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.
In Splunk Enterprise 10.2 versions below 10.2.4 and 10 versions below 10.0.7, an unauthenticated user could create or truncate arbitrary files through a PostgreSQL sidecar service endpoint.…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-06-18. Federal agencies were required to remediate by 2026-06-21.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2026-20253.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Description
In Splunk Enterprise 10.2 versions below 10.2.4 and 10 versions below 10.0.7, an unauthenticated user could create or truncate arbitrary files through a PostgreSQL sidecar service endpoint. The vulnerability exists because the PostgreSQL sidecar service endpoint lacks authentication controls, allowing any network-reachable user to invoke file operations without credentials. Splunk Enterprise versions 9.4 and earlier are not affected. If you cannot immediately upgrade to a fixed version, you can mitigate this vulnerability by disabling the PostgreSQL sidecar service.
Affected Products
splunksplunkResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every splunk splunk deployment and check each version against the affected-products list above.
Fix
Apply the splunk splunk security patch or hotfix for CVE-2026-20253 on the affected version, following the vendor advisory for your exact build.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2026-20253
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2026-20253 -u https://target- Template
- Splunk Enterprise & Cloud Platform - Unrestricted File Upload
- Severity
- critical
- Impact
- Unauthenticated attackers can create or truncate arbitrary files, potentially leading to data loss or system compromise.
- Remediation
- Upgrade to Splunk Enterprise 10.2.4, 10.0.7 and Splunk Cloud Platform 10.4.2604.3, 10.2.2510.14 or later.
Template by ProjectDiscovery nuclei-templates (watchtowrlabs, DhiyaneshDk), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2026-20253 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.