Summary
oban_web: Unbounded range expansion in cron describe causes memory exhaustion
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
- Schedule a cron job with expression
"0 0 1-100000000 * *"(or any expression with an out-of-domain range). - Have any user with Oban.Web dashboard access navigate to the cron job list.
- The dashboard calls
describe/1to render the expression, exhausting BEAM memory and crashing the node.
References
Impact
CVSS 4.0 score 5.9 (Medium). Affects oban_web >= 2.12.0. Requires the ability to schedule a cron job and a dashboard user to view the cron list; no further privileges are needed.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-48593? CVE-2026-48593 is a medium-severity uncontrolled resource consumption vulnerability in oban_web (erlang), affecting versions >= 2.12.0, < 2.12.5. It is fixed in 2.12.5. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- Which versions of oban_web are affected by CVE-2026-48593? oban_web (erlang) versions >= 2.12.0, < 2.12.5 is affected.
- Is there a fix for CVE-2026-48593? Yes. CVE-2026-48593 is fixed in 2.12.5. Upgrade to this version or later.
- Is CVE-2026-48593 exploitable, and should I be worried? Whether CVE-2026-48593 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-48593 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-48593? Upgrade
oban_webto 2.12.5 or later.