Derived-key recovery via early-exit string comparison
Published Jun 12, 2026 · Updated Jun 12, 2026
Observable timing discrepancies in Crypt::PBKDF2 before 0.261630 allow remote attackers to recover derived keys during validation. Crypt::PBKDF2::validate compares the computed and supplied hashes with Perl's early-exit eq operator, so response time reveals how much of a candidate matches. The attack requires repeated, precisely timed validation attempts; it exposes derived-key material without changing stored data or interrupting service.
Summary
What happened
Observable timing discrepancies in Crypt::PBKDF2 before 0.261630 allow remote attackers to recover derived keys during validation. Crypt::PBKDF2::validate compares the computed and supplied hashes with Perl's early-exit eq operator, so response time reveals how much of a candidate matches. The attack requires repeated, precisely timed validation attempts; it exposes derived-key material without changing stored data or interrupting service.
The record
- CVE
- CVE-2017-20240
- Published
- Jun 12, 2026
- Updated
- Jun 12, 2026
- Vendor
- Andrew Rodland
- Product
- Crypt::PBKDF2
- Classifications
- CWE-208, T1110
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 12, 2026CVE publishedPublication date reported by the CVE source.
- Jun 12, 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?
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- Affected versionversion=0 <0.261630
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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Public exploit references
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Technologies
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Your stack
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