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EUVD-2026-322096

fkie_cve-2026-48593

Uncontrolled Resource Consumption vulnerability in oban-bg oban_web ('Elixir.Oban.Web.CronExpr' modules) allows memory exhaustion via unbounded cron range expansion.

An attacker with access to schedule cron jobs can submit a malicious cron expression such as "0 0 1-100000000 * *". When a user with dashboard access views the cron job list, 'Elixir.Oban.Web.CronExpr':describe/1 is called to render the expression. parse_range/1 parses both range endpoints via Integer.parse/1 with no bounds check, and the downstream helpers expand_dom_parts/1 and expand_dow_parts/1 materialise the range eagerly via Enum.to_list/1, causing allocation of ~2.4 GB and stalling or crashing the BEAM node. A sibling helper extract_dom_values already validates range bounds, but the expansion helpers do not.

This issue affects oban_web: from 2.12.0 before 2.12.5.

GHSA-6xh2-93p9-vqh4 — oban_web: Unbounded range expansion in cron describe causes memory exhaustion

Affected: Hex: oban_web

### Summary

`oban_web` 2.12.0 introduced a cron expression parser that expands `-`-separated ranges without validating the endpoints. An attacker with access to schedule cron jobs can submit a malicious expression; when any user with dashboard access views the cron job list, `Oban.Web.CronExpr.describe/1` is called to render it, triggering allocation of gigabytes of memory and stalling or crashing the BEAM node.

### Details

**1. Scheduling:** The attacker submits a cron job with a malicious expression such as `"0 0 1-100000000 * *"`. No special privilege is required beyond the ability to schedule cron jobs.

**2. Parsing:** When the cron list is rendered in the dashboard, `describe/1` calls `parse_range/1` in `lib/oban/web/cron_expr.ex`, which calls `Integer.parse/1` on both endpoints of the range with no bounds check, returning `{:range, start_val, end_val}` for any integers.

**3. Eager expansion:** `expand_dom_parts/1` and `expand_dow_parts/1` materialise the range via `Enum.to_list(start_val..end_val)`. The input above produces ~100 million integers (~2.4 GB). A sibling helper `extract_dom_values` already validates range bounds, but the expansion helpers do not.

### PoC

1. Schedule a cron job with expression `"0 0 1-100000000 * *"` (or any expression with an out-of-domain range). 2. Have any user with Oban.Web dashboard access navigate to the cron job list. 3. The dashboard calls `describe/1` to render the expression, exhausting BEAM memory and crashing the node.

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