YAFNET: Pre-Handler Authorization Bypass on Admin Pages Enables Blind SQL Execution via /Admin/RunSql

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.8 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-43937: 0.49% estimated exploitation activity in the next 30 days; percentile 42.12 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Issue Details: YAFNET's only admin authorization gate is PageSecurityCheckAttribute, implemented as a ResultFilterAttribute that runs after the page handler completes rather than before it. No other gate exists. Any admin OnPost… handler therefore executes its side effects before the filter rewrites the response to a 302 to /Info/4. The most impactful abuse is /Admin/RunSql, whose OnPostRunQuery binds Editor from the POST body and passes it straight to IDbAccess.RunSql with no caller check, yielding arbitrary SQL execution for any low-privileged user. A deterministic boolean-conditional time oracle was confirmed end-to-end by extracting the first character of @@VERSION: IF (ASCII(SUBSTRING(@@VERSION, 1, 1)) = 77) WAITFOR DELAY '0:0:5' produced a ~5-second delay (confirming the byte is M), while IF (ASCII(SUBSTRING(@@VERSION, 1, 1)) = 76) WAITFOR DELAY '0:0:5' returned immediately. Impact: An attacker holding the lowest-privileged authenticated role, effectively an anonymous attacker…

Published by the source

5 May 2026, 20:32 UTC

Last modified by the source

13 May 2026, 16:24 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-xhw7-j96h-c3g5

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# Patch Next advisory brief: CVE-2026-43937

Advisory: YAFNET: Pre-Handler Authorization Bypass on Admin Pages Enables Blind SQL Execution via `/Admin/RunSql`
IDs: CVE-2026-43937, GHSA-xhw7-j96h-c3g5
Record: https://patchnext.com/advisories/cve-2026-43937 (revision 1, source checked 26 Oct 2026, 17:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: yafnet.core 4.0.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet yafnet.core: affected <= 4.0.4; fixed in 4.0.5

## Suggested inspection (read-only)
- NuGet yafnet.core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on yafnet.core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-xhw7-j96h-c3g5 (GitHub-reviewed advisory GHSA-xhw7-j96h-c3g5 lists affected ranges: NuGet yafnet.core >=0 <=4.0.4)

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