CVE-2026-53525: WeeChat has Non-Constant-Time Password Hash Comparison in Relay Authentication
Vulnerability summary
CVE-2026-53525 is a high (CVSS 7.4) Observable Timing Discrepancy vulnerability in weechat. EPSS estimates a 0.43% chance of exploitation in the next 30 days, higher than 36.3% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 2 · Related 2Timeline
- 21-08-2026PublishedVulnerability first disclosed.
- 25-08-2026Last modifiedVulnerability information updated.
Description
WeeChat (Wee Enhanced Environment for Chat) is a free chat client. In versions 0.3.1 through 4.9.0, the WeeChat relay authentication uses non-constant-time string comparison functions (weechat_strcasecmp and strcmp) to verify password hashes and plaintext passwords. An attacker can exploit timing differences to extract the server-computed hash character by character, then authenticate using the correct hash without knowing the password. Version 4.9.1 fixes the issue.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
- OSV · DebianEcosystem advisory · calculated7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
- NVDNIST7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
EPSS trend
Probability
0.43%
Chance of exploitation in the next 30 days
Percentile
36%
Versus all other CVEs
30-day change
Increase +0.18 pp
From 0.25% on 22-09-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian1 product
- weechatAll versions (No fix recorded) | < 4.9.3-1
Ubuntu1 product
- weechatAll versions (No fix recorded)
Weechat1 product
- weechat≥ 0.3.4, < 4.9.1
3 vendors · 3 products
