Forged billing webhooks via timing-leaky HMAC comparison
Published Sep 14, 2026 · Updated Sep 14, 2026
Observable timing discrepancy in pay-rails Pay 11.6.1 and earlier allows remote attackers to forge Paddle Billing webhooks. The valid_signature? method compares a computed SHA-256 HMAC with the header's h1 token using short-circuiting String#==, exposing matching prefixes through response timing. Exploitation requires many precise measurements against the public webhook route; a recovered signature can enqueue attacker-chosen events that alter billing state or provision paid features.
Summary
What happened
Observable timing discrepancy in pay-rails Pay 11.6.1 and earlier allows remote attackers to forge Paddle Billing webhooks. The valid_signature? method compares a computed SHA-256 HMAC with the header's h1 token using short-circuiting String#==, exposing matching prefixes through response timing. Exploitation requires many precise measurements against the public webhook route; a recovered signature can enqueue attacker-chosen events that alter billing state or provision paid features.
The record
- CVE
- CVE-2026-70658
- Published
- Sep 14, 2026
- Updated
- Sep 14, 2026
- Vendor
- Yansongda
- Product
- Pay
- Classifications
- CWE-208, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 14, 2026CVE publishedPublication date reported by the CVE source.
- Sep 14, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 11.6.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-mjgf-xj26-9qf9 timing-oracle proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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