CVE-2026-48593: oban_web Unbounded Range Expansion Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6xh2-93p9-vqh4",
  "modified" : "2026-06-30T18:32:49Z",
  "published" : "2026-06-30T18:32:49Z",
  "aliases" : [ "CVE-2026-48593" ],
  "summary" : "oban_web: Unbounded range expansion in cron describe causes memory exhaustion",
  "details" : "### Summary\n\n`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.\n\n### Details\n\n**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.\n\n**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.\n\n**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.\n\n### PoC\n\n1. Schedule a cron job with expression `\"0 0 1-100000000 * *\"` (or any expression with an out-of-domain range).\n2. Have any user with Oban.Web dashboard access navigate to the cron job list.\n3. The dashboard calls `describe/1` to render the expression, exhausting BEAM memory and crashing the node.\n\n### Impact\n\nCVSS 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.\n\n### References\n\n* Introduction commit: https://github.com/oban-bg/oban_web/commit/a97c7960bb389b05aaab4cf8042985f02ceddc24\n* Patch commit: https://github.com/oban-bg/oban_web/commit/9998b7e284e02fdd4645dd6231760038e63b584d",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Hex",
      "name" : "oban_web"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.12.0"
      }, {
        "fixed" : "2.12.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/oban-bg/oban_web/security/advisories/GHSA-6xh2-93p9-vqh4"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-48593"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/oban-bg/oban_web/commit/9998b7e284e02fdd4645dd6231760038e63b584d"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/oban-bg/oban_web/commit/a97c7960bb389b05aaab4cf8042985f02ceddc24"
  }, {
    "type" : "WEB",
    "url" : "https://cna.erlef.org/cves/CVE-2026-48593.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/oban-bg/oban_web"
  }, {
    "type" : "WEB",
    "url" : "https://osv.dev/vulnerability/EEF-CVE-2026-48593"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-30T18:32:49Z",
    "nvd_published_at" : "2026-05-26T21:16:41Z"
  }
}