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

Quick assessment

Affected
pay-rails pay
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Pay是Pay组织开源的一款提供支付交易处理能力的软件组件。 Pay 11.6.2之前版本存在侧信道信息泄露漏洞，该漏洞源于Pay::Webhooks::PaddleBillingController#valid_signature?使用Ruby String#==将计算的64字符SHA-256 HMAC与来自Paddle-Signature标头的攻击者可控h1令牌进行比较，未经身份验证的远程攻击者可通过反复提交请求并获取精确的时间差异，推断匹配的摘要前缀并恢复有效签名，伪造的webhook经Pay::W

CVSS 7.4 · High EPSS 0.50% · P42

Affected Version Matrix 1

VendorProduct Version RangeStatus
pay-rails pay < 11.6.2 affected
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I. Basic Information for CVE-2026-70658

Vulnerability Information
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Vulnerability Title
pay-rails/pay: non-constant-time HMAC comparison in Paddle Billing webhook signature verifier
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过时间差异性导致的信息暴露
Source: CVE Program / CVE List V5
Vulnerability Title
Pay 侧信道信息泄露漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Pay是Pay组织开源的一款提供支付交易处理能力的软件组件。 Pay 11.6.2之前版本存在侧信道信息泄露漏洞，该漏洞源于Pay::Webhooks::PaddleBillingController#valid_signature?使用Ruby String#==将计算的64字符SHA-256 HMAC与来自Paddle-Signature标头的攻击者可控h1令牌进行比较，未经身份验证的远程攻击者可通过反复提交请求并获取精确的时间差异，推断匹配的摘要前缀并恢复有效签名，伪造的webhook经Pay::W
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
pay-rails pay < 11.6.2 -

II. Public POCs for CVE-2026-70658

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III. Intelligence Information for CVE-2026-70658

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Patches & Fixes for CVE-2026-70658 (1)

Vendor Advisories for CVE-2026-70658 (1)

Vendor Pages for CVE-2026-70658 (1)

IV. Related Vulnerabilities

Same product: pay
Same vendor: pay-rails
Same weakness: CWE-208

V. Comments for CVE-2026-70658

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