CVE-2026-82760

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Description

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.

Weaknesses & attack patterns

Weakness

CWE-407 · Inefficient Algorithmic Complexity in catalog → MITRE ↗

Attack patterns

CAPEC-130 · Excessive Allocation MITRE ↗

Affected — Hex / ash_authentication Hex.pm ↗ Repository ↗

≥ 4.8.0 < 4.15.0 affected

5.0 series ≥ 5.0.0-rc.0 < 5.0.0-rc.14 affected

every other version: unaffected

cpe cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*

modules · source files · routines

modules 'Elixir.AshAuthentication.Base' · 'Elixir.AshAuthentication.Strategy.ApiKey.SignInPreparation'

source files lib/ash_authentication/base.ex · lib/ash_authentication/strategies/api_key/sign_in_preparation.ex

routines 'Elixir.AshAuthentication.Base':decode62/1 · 'Elixir.AshAuthentication.Base':bindecode62/1 · 'Elixir.AshAuthentication.Strategy.ApiKey.SignInPreparation':prepare/3

Affected — GitHub / team-alembic/ash_authentication Repository ↗

≥ f3a53f4 and up affected