CVE-2026-20253
Splunk Enterprise Missing Authentication for Critical Function Vulnerability
Splunk Enterprise
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.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 18 June 2026. US federal agencies were required to remediate it by 21 June 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 96.9%, which is higher than 99.9% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Frequently asked questions
Is CVE-2026-20253 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2026-20253.
What does CVE-2026-20253 affect?
CVE-2026-20253 affects Splunk Enterprise. 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.
How severe is CVE-2026-20253?
CVE-2026-20253 is rated CRITICAL with a CVSS base score of 9.8. EPSS puts the probability of exploitation in the next 30 days at 96.9%, higher than 99.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 21 June 2026.
How should organisations respond to CVE-2026-20253?
Apply the vendor patch for Splunk Enterprise as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.