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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-70658
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-14 18:19:45 UTC
Updated2026-09-14 19:17:40 UTC
DescriptionPay 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.

Risk And Classification

Primary CVSS: v3.1 7.4 HIGH from [email protected]

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

Problem Types: CWE-208 | CWE-208 CWE-208: Observable Timing Discrepancy

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
3.1CNADECLARED7.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Pay-rails Pay affected < 11.6.2 Not specified

References

ReferenceSourceLinkTags
github.com/pay-rails/pay/releases/tag/v11.6.2 [email protected] github.com
github.com/pay-rails/pay/commit/ba6494109d88209fba2a4df2d9d6373fe81ed805 [email protected] github.com
github.com/pay-rails/pay/security/advisories/GHSA-mjgf-xj26-9qf9 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
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