Bearer token length disclosure via timing
Published Jul 14, 2022 · Updated Apr 23, 2025
Observable timing discrepancy in Fastify @fastify/bearer-auth before 7.0.2 and 8.0.1 allows remote attackers to infer bearer-token length. The plugin compares supplied bearer tokens with configured keys using crypto.timingSafeEqual, but unequal-length inputs return through a measurably different path. Unauthenticated network requests can exploit this side channel to narrow brute-force guesses of a valid base64 bearer token; no direct token disclosure or service interruption is established.
Summary
What happened
Observable timing discrepancy in Fastify @fastify/bearer-auth before 7.0.2 and 8.0.1 allows remote attackers to infer bearer-token length. The plugin compares supplied bearer tokens with configured keys using crypto.timingSafeEqual, but unequal-length inputs return through a measurably different path. Unauthenticated network requests can exploit this side channel to narrow brute-force guesses of a valid base64 bearer token; no direct token disclosure or service interruption is established.
The record
- CVE
- CVE-2022-31142
- Published
- Jul 14, 2022
- Updated
- Apr 23, 2025
- Vendor
- Fastify
- Product
- @fastify/bearer-auth
- Classifications
- CWE-208
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 14, 2022CVE publishedPublication date reported by the CVE source.
- Apr 23, 2025Record 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=>= 5.0.1, < 7.0.2
- Affected versionversion== 8.0.0
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
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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