Superlinear base62 decoding exhausts CPU and memory in AshAuthentication API key sign-in
Published Sep 17, 2026 · Updated Sep 17, 2026
Inefficient Algorithmic Complexity vulnerability in team-alembic AshAuthentication allows an unauthenticated attacker to exhaust CPU and memory via an oversized base62 segment in a submitted API key.
Summary
What happened
Inefficient Algorithmic Complexity vulnerability in team-alembic AshAuthentication allows an unauthenticated attacker to exhaust CPU and memory via an oversized base62 segment in a submitted API key.
AshAuthentication.Base.decode62/1 in lib/ash_authentication/base.ex splits its argument into one binary per character and folds it with charval62/2, which recomputes Integer.pow(62, index) at every position instead of accumulating by Horner's method, so cost grows roughly cubically in the input length. bindecode62/1 in the same module is quadratic through Integer.undigits/2 and Integer.digits/2. Neither function caps byte_size/1, and AshAuthentication.Strategy.ApiKey.SignInPreparation passes the underscore-separated segments of the submitted key straight into both, before any key lookup and without prior authentication. The surrounding rescue clauses catch exceptions, not CPU or memory exhaustion.
This issue affects ash_authentication: from 4.8.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.
The record
- CVE
- CVE-2026-82760
- Published
- Sep 17, 2026
- Updated
- Sep 17, 2026
- Vendor
- Alembic
- Product
- Ash Authentication
- Classifications
- Unavailable
- Attack vector
- Unavailable
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 17, 2026CVE publishedPublication date reported by the CVE source.
- Sep 17, 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=4.8.0 <4.15.0
- Affected versionversion=5.0.0-rc.0 <5.0.0-rc.14
- Affected versionversion=f3a53f480088419788d5c3934af3131fa9066773 <* changes=[{"at":"d5a5d4cb5cc17fbd6e2a120a6111b47accad4b8e","status":"unaffected"},{"at":"dfb19c897853686ab481c5e773f7a1a0c74dea04","status":"unaffected"}]
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What is affected?
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Attacks
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Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Activity data is delayed. The latest report is Sep 28, 2026.
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