CVE-2026-20253: Splunk Enterprise Missing Authentication for Critical Function Vulnerability

In short

Splunk Enterprise has a weakness classified as missing authentication for critical function (CWE-306). CISA added it to its Known Exploited Vulnerabilities catalog on 2026-06-18. NVD lists CVSS 3.1 at 9.8 CRITICAL.

What it is

“Splunk Enterprise contains a missing authentication for critical function vulnerability which could allow an unauthenticated user to create or truncate arbitrary files through a PostgreSQL sidecar service endpoint.” — CISA KEV, retrieved 2026-11-01

“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.” — NVD, retrieved 2026-11-01

Who is affected

Splunk Enterprise. NVD lists the following versions as affected:

• Versions from 10.0.0 inclusive, before 10.0.7
• Versions from 10.2.0 inclusive, before 10.2.4

Exploitation status

CISA KEV added: 2026-06-18. Known ransomware campaign use: Not reported by CISA. Due date CISA set for US federal civilian agencies: 2026-06-21.

Scores

NVD CVSS 3.1: 9.8 CRITICAL; vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source [email protected].

EPSS by FIRST: 96.94%; percentile 99.89; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-306.

Timeline

CISA required action

“Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.” — CISA KEV

What to do

• Confirm whether you run Splunk Enterprise and which version.
• Apply the vendor update or mitigation in the advisory.
• Follow CISA’s required action.
• Review the vendor guidance on signs of compromise.
• Track the fix through completion.

References

• Mitigation, Vendor Advisory: https://advisory.splunk.com/advisories/SVD-2026-0603
• NVD detail
• CVE.org record
• CISA KEV catalog

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.