High 7.4Published Sep 14, 2026

CVE-2026-70658pay-rails/pay: non-constant-time HMAC comparison in Paddle Billing webhook signature verifier

Updated under an hour ago (2026-10-19 09:40 UTC)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

Pay is a payments engine for Ruby on Rails 6.0 and higher. Prior to 11.6.2, Pay::Webhooks::PaddleBillingController#valid_signature? in app/controllers/pay/webhooks/paddle_billing_controller.rb compares the computed 64-character SHA-256 HMAC with the attacker-controlled h1 token from the Paddle-Signature header using Ruby String#==. An unauthenticated remote attacker who can repeatedly submit requests to /pay/webhooks/paddle_billing and obtain sufficiently precise timing measurements can infer matching digest prefixes and recover a valid signature. A forged accepted webhook is enqueued through Pay::Webhooks::ProcessJob and can cause a host application to update billing state, provision paid features, record refunds, or trigger customer notifications. This issue is fixed in version 11.6.2.

CVSS: 7.4 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness (CWE): CWE-208
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Awaiting Analysis
Record last updated: Sep 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

pay-rails pay pay_rails:pay (from the name)	before 11.6.2	CNA record

References

https://github.com/pay-rails/pay/security/advisories/GHSA-mjgf-xj26-9qf9x-refsource-confirm
https://github.com/pay-rails/pay/commit/ba6494109d88209fba2a4df2d9d6373fe81ed805x-refsource-misc
https://github.com/pay-rails/pay/releases/tag/v11.6.2x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.