CVE-2026-82760: Superlinear base62 decoding exhausts CPU and memory in AshAuthentication API key sign-in
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/ashauthentication/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 bytesize/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 ashauthentication: from 4.8.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.
Affected Software
Event History
Frequently Asked Questions
Which releases require remediation?
Affected releases are ash_authentication 4.8.0 through versions before 4.15.0, and 5.0.0-rc.0 through versions before 5.0.0-rc.14.
Does exploitation require an account or a valid API key?
No. An unauthenticated attacker can submit a crafted API key, and decoding occurs before key lookup or any prior authentication.
What input reaches the vulnerable code path?
The API key sign-in preparation processes underscore-separated segments from the submitted key directly with the affected decoding functions. An oversized base62 segment can drive excessive CPU and memory consumption.
Will the existing exception handling stop a denial-of-service attempt?
No. The surrounding rescue clauses catch exceptions, but they do not handle CPU or memory exhaustion.