Add vulnerability detection module for CVE-2026-20253 (Splunk Enterprise unauthenticated auth-bypass) - #1665
Add vulnerability detection module for CVE-2026-20253 (Splunk Enterprise unauthenticated auth-bypass)#1665NSK-394 wants to merge 6 commits into
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WalkthroughAdded a Splunk CVE-2026-20253 vulnerability module. The module sends a non-destructive recovery backup request and detects the authentication-bypass response. The module catalog documents the new module. ChangesVulnerability module updates
Estimated code review effort: 2 (Simple) | ~10 minutes Merge Risk: ⚪ Minimal · up to This PR adds a localized Splunk vulnerability check and documentation entry; no actionable merge-blocking risk remains beyond normal checks and review. Suggested labels: Suggested reviewers: 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
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✨ Finishing Touches🧪 Generate unit tests (beta)
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@securestep9 @arkid15r This is available for review whenever you have a moment |
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@securestep9 Here's the module running against a real vulnerable target |
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malformed-request validation error instead of creating a real backup job Previous version's success condition (status 200 + BackupPending) proved a real backup job was created on the vulnerable target on every scan, contradicting the module's own non-destructive claim (caught by Codex review). Fixed by omitting the backupFile field entirely -- vulnerable instances bypass auth and reach field validation (400 + specific error message), while patched instances reject on auth before ever reaching validation (401), regardless of body content. Verified stable across 8 repeated attempts on the vulnerable side and 8 attempts (including 3 additional malformed-variant checks) on the patched side, with zero job creation confirmed in both cases.
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Actionable comments posted: 1
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Inline comments:
In `@nettacker/modules/vuln/splunk_cve_2026_20253.yaml`:
- Line 62: Update the request headers near the database request to use the
scanner’s {user_agent} placeholder instead of the fixed Nettacker User-Agent
value, while keeping the request body and TemplateLoader.format-compatible JSON
unchanged.
Apply the same fix in `@nettacker/modules/vuln/splunk_cve_2026_20253.yaml` at line
58.
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Update on #1673 -- turns out this is expected behavior, not a bug: |
2 participants
Closes #1664
Proposed change
New vulnerability detection module for CVE-2026-20253 (CVSS 9.8, added to
CISA's Known Exploited Vulnerabilities catalog) — a missing-authentication
flaw (CWE-306) in Splunk Enterprise's bundled PostgreSQL sidecar service.
The sidecar is reachable through an unauthenticated raw-passthrough proxy
path on Splunk Web (default port 8000):
POST /en-US/splunkd/__raw/v1/postgres/recovery/backup. Splunk Enterprise10.0.0-10.0.6 and 10.2.0-10.2.3 accept this request with ANY
syntactically-valid HTTP Basic Authorization header — including a blank
:credential or entirely fabricated ones — because the credential valueitself is never validated. Patched versions (10.0.7, 10.2.4, 10.4.0+)
reject the identical request, having dropped Basic-auth support on this
endpoint entirely.
This is a single-request module: one POST with a blank Basic auth header,
checking for
status_code == 200and"state":"BackupPending"in theresponse body. No multi-step chaining or
dependent_on_temp_eventneeded.Verification: confirmed live against the official
splunk/splunk:10.0.6(vulnerable) and
splunk/splunk:10.0.7(patched) Docker images beforewriting any module code, resolving a real contradiction found in secondary
sources about the exact vulnerable-response signature:
200 OK+{"state":"BackupPending", ...}401 Unauthorized+"Authorization header must use Splunk token"Confirmed stable across repeated requests on both
/backupand/restore.Loaded and expanded cleanly through
TemplateLoader+expand_module_steps(6 sub-requests: http/https × 8000/80/443), andverified end-to-end via the real Nettacker CLI against both containers —
vulnerable target correctly shows
Detected, patched target correctlyshows no detection with no false positive.
Detection scope: this module confirms the unauthenticated auth-bypass
primitive — the CVE's actual root cause. It does not attempt or verify the
further chained RCE some public writeups describe, which additionally
requires standing up an attacker-controlled external PostgreSQL server and
waiting on Splunk's own task scheduler to execute a planted file. That
chain is out of scope for a safe, non-destructive scanner check.
Type of change
Checklist
make pre-commitand confirm it didn't generate anywarnings/changes (
makeunavailable on Windows; ran the modulethrough TemplateLoader/expand_module_steps directly — zero errors)
make testand I confirm all tests passed locally (rantests/test_yaml_schema_and_regex.pydirectly: this module passes;127 passed / 6 skipped total; the 1 unrelated failure is a
pre-existing Windows-encoding issue in
subdomain_takeover.yaml,unconnected to this change)
docs/folderthe issue as described (see Verification section above)
intended (see comment below with live scan output against a real
vulnerable Splunk 10.0.6 container)
unreviewed outputs of AI
code, comment, and design decision