Unbounded range expansion in cron describe causes memory exhaustion in oban_web

Weakness Type (CWE)

CWE-400 — CWE-400 Uncontrolled Resource Consumption

CAPEC

CAPEC-130 — CAPEC-130 Excessive Allocation

CVSS 4.0 Score

5.9

MEDIUM

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Vulnerability description

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.

Affected

`pkg:hex/oban_web`

Module	Source File	Routine
`Oban.Web.CronExpr`	`lib/oban/web/cron_expr.ex`	`Oban.Web.CronExpr.describe/1`
		`Oban.Web.CronExpr.parse_range/1`
		`Oban.Web.CronExpr.expand_dom_parts/1`
		`Oban.Web.CronExpr.expand_dow_parts/1`

Status	Type	Version	Changes / Fixed in
affected	semver ^ⓘ	`2.12.0`	< `2.12.5`

`pkg:github/oban-bg/oban_web`

Module	Source File	Routine
`Oban.Web.CronExpr`	`lib/oban/web/cron_expr.ex`	`Oban.Web.CronExpr.describe/1`
		`Oban.Web.CronExpr.parse_range/1`
		`Oban.Web.CronExpr.expand_dom_parts/1`
		`Oban.Web.CronExpr.expand_dow_parts/1`

Status	Type	Version	Changes / Fixed in
affected	git ^ⓘ	`a97c7960bb`	< `9998b7e284`

Configurations

The vulnerability is exploitable when an attacker with access to schedule cron jobs submits a malicious cron expression. The crash is triggered when a user with dashboard access views the cron job list, which calls 'Elixir.Oban.Web.CronExpr':describe/1 to render the expression.

References

https://github.com/oban-bg/oban_web/security/advisories/GHSA-6xh2-93p9-vqh4 vendor-advisory related
https://osv.dev/vulnerability/EEF-CVE-2026-48593 related
https://github.com/oban-bg/oban_web/commit/9998b7e284e02fdd4645dd6231760038e63b584d patch

Credits

Finder: Peter Ullrich
Remediation developer: Shannon Selbert
Analyst: Jonatan Männchen

CVE record as JSON: GET /cves/CVE-2026-48593.json
OSV record as JSON: GET /osv/EEF-CVE-2026-48593.json