CVE-2026-20253

Exploitation: active CVSS 9.8 CRITICAL

CVSS base score: 9.8 (Critical) vendor CNA · v3.1

Score assigned by the vendor's own CVE Numbering Authority (CNA); CISA's Vulnrichment program adds a score only when the CNA omits one.

Splunk Enterprise Missing Authentication for Critical Function Vulnerability

Vendor: Splunk Product: Enterprise

Description

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.

Lifecycle Timeline

2026-06-10

CVE published

Entered the public CVE record.

CVE.org →
2026-06-12

Public exploit code 2 days later

Public GitHub repository watchtowrlabs/watchTowr-vs-Splunk-CVE-2026-20253 — unvetted, may contain malware

GitHub PoC →
2026-06-18

Added to CISA KEV 6 days later

Listed as known exploited, which starts the federal remediation clock.

CISA KEV →
2026-06-21

Federal remediation due 3 days later

Deadline for federal civilian agencies under BOD 22-01 — now passed.

CISA KEV
2026-06-27

EPSS flags exploitation risk 6 days later

Probability jumped from 10.0% to 88.2%. Dated to the sampled week.

FIRST EPSS →
not recorded

First national advisory

No tracked government advisory analyses this CVE. Routine KEV catalog-addition alerts do not count here.
not recorded

Vendor fix published

No dated vendor fix. Only Microsoft publishes a machine-readable release date; other vendors state a fixed version without one.

Each milestone comes from a different source, so gaps between them are gaps in what those sources publish, not evidence that nothing happened. EPSS history for this CVE holds 27 points from 2026-06-13, tracked daily from 2026-09-09; earlier points are weekly, which dates a spike to within a week. Peak probability 96.9% on 2026-08-08.

Published Applicability

CVE List v5 (CNA container) 2 affected · 0 fixed · 0 not affected

Check whether a specific version is affected →

What each source publishes about which product versions carry this vulnerability, kept as written rather than merged. Absence here means no source has published applicability data, not that nothing is affected.

Research & News Coverage

Date	Source	Article
2026-06-30	FortiGuard Labs Threat Signal	Splunk Enterprise Authentication Bypass Vulnerability

Articles from monitored vendor research blogs and security news feeds that specifically mention this CVE. Coverage begins when feed monitoring started; earlier articles are not indexed.

Detection & Exploitation

Scan

Nuclei

Exploit / Pen Test

GitHub PoC7

Network IDS/IPS

none published

Host / SIEM

none published

Coverage across public collections only: Nuclei and OpenVAS NVT (scan); Snort and Suricata ET Open (network); Sigma and YARA (host/SIEM); Metasploit, Exploit-DB and public GitHub repositories (exploit). Absence here means nothing public was found, not that detection is impossible.
GitHub PoC repositories are collected automatically by PoC-in-GitHub (CC0) and are not vetted: some are fakes and some are malware. Treat them as evidence that code was published, not as code to run.
OpenVAS coverage derives from the Greenbone Community Feed, made available under the Open Database License (ODbL) v1.0; its individual Vulnerability Tests are licensed GNU GPL v2.

CISA Assessment (Vulnrichment / SSVC)

Exploitation

active

Automatable

yes

Technical impact

total

CVSS — CISA

—

CVSS — vendor CNA 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

Weakness

CWE-306 — The software does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.

Assessment updated

2026-06-10

D3FEND Countermeasures

Defensive techniques inferred by MITRE D3FEND from the underlying weakness (CWE-306) — general hardening and detection guidance for this weakness class, not a vendor patch for this specific CVE.

Model

Asset Vulnerability Enumeration Software Inventory

Harden

Credential Scrubbing Domain Logic Validation Software Update Trusted Library Variable Initialization

Isolate

Application-based Process Isolation

Restore

Restore Software

KEV Catalog Status

Added to KEV

2026-06-18

BOD 22-01 due date

2026-06-21

Known ransomware use

Unknown

Listed By

Source	Date	Record
CISA Vulnrichment	2026-06-10	source record →
CISA KEV	2026-06-18	source record →

Referenced in Advisories

Date	Advisory	Issuer
2026-06-18	CISA Adds One Known Exploited Vulnerability to Catalog	CISA

Weaponization Timeline — Offensive & Testing Tools

Date	Tool	Evidence quality	Reference
2026-06-12	Nuclei	Direct — curated exploit code	CVE-2026-20253.yaml

Evidence tiers are explained on the About page — a merged Metasploit module is far stronger evidence than a distro package mention.

External References

CVE.org record → NVD entry → CISA KEV catalog → FortiGuard Labs → Rapid7 AttackerKB →

⚠ Known Exploited Vulnerability (KEV) Tracker