Authentication bypass via early-exit password comparisons
Published Aug 21, 2026 · Updated Aug 25, 2026
Observable timing discrepancy in WeeChat 0.3.4 through 4.9.0 allows remote attackers to bypass Relay authentication over a network. Relay authentication compares encoded SHA or PBKDF2 hashes with weechat_strcasecmp and plaintext passwords with strcmp, exiting on the first mismatch. Repeated measurements over localhost or a LAN reveal the server-computed hash character by character; the recovered hash grants an authenticated Relay session.
Summary
What happened
Observable timing discrepancy in WeeChat 0.3.4 through 4.9.0 allows remote attackers to bypass Relay authentication over a network. Relay authentication compares encoded SHA or PBKDF2 hashes with weechat_strcasecmp and plaintext passwords with strcmp, exiting on the first mismatch. Repeated measurements over localhost or a LAN reveal the server-computed hash character by character; the recovered hash grants an authenticated Relay session.
The record
- CVE
- CVE-2026-53525
- Published
- Aug 21, 2026
- Updated
- Aug 25, 2026
- Vendor
- WeeChat
- Product
- WeeChat
- Classifications
- CWE-208, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 21, 2026CVE publishedPublication date reported by the CVE source.
- Aug 25, 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=>= 0.3.4, < 4.9.1
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
- Relay authentication timing attack procedureproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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