RUSTSEC-2026-0433

Vulnerability from osv_rustsec – Published: 2026-10-28 12:00 – Updated: 2026-11-02 11:17 – Source website
VLAI
Summary
Quadratic parsing of nested image wikilinks with `ENABLE_WIKILINKS`
Details

With Options::ENABLE_WIKILINKS, handle_wikilink builds a wikilink's target from the raw text of its body: scan_wikilink_pipe walks it looking for |, then contains('\0') and from_replace_nuls walk it again. Once a wikilink is created, disable_all_links only disables Link entries, so every enclosing ![[ stays live on the wikilink stack. On ![[![[![[…]]]]]] each of those openers then resolves in turn and rescans everything inside it, which is quadratic in the nesting depth. The event count stays tiny, because in the unpiped case each enclosing image replaces its body with a fresh text node, so all of that work is thrown away.

Applications that parse untrusted Markdown with ENABLE_WIKILINKS set, including through Options::all(), are affected. The option is off by default. Parsing without it is not affected.

The flaw was fixed in #1186 and released in 0.13.6.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "categories": [
          "denial-of-service"
        ],
        "cvss": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
        "informational": null
      },
      "ecosystem_specific": {
        "affected_functions": null,
        "affects": {
          "arch": [],
          "functions": [],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "pulldown-cmark",
        "purl": "pkg:cargo/pulldown-cmark"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.13.0"
            },
            {
              "fixed": "0.13.6"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "With `Options::ENABLE_WIKILINKS`, handle_wikilink builds a wikilink\u0027s target\nfrom the raw text of its body: scan_wikilink_pipe walks it looking for |, then\ncontains(\u0027\\0\u0027) and from_replace_nuls walk it again.\nOnce a wikilink is created, disable_all_links only disables Link entries, so\nevery enclosing `![[` stays live on the wikilink stack.\nOn `![[![[![[\u2026]]]]]]` each of those openers then resolves in turn and rescans\neverything inside it, which is quadratic in the nesting depth.\nThe event count stays tiny, because in the unpiped case each enclosing image\nreplaces its body with a fresh text node, so all of that work is thrown away.\n\nApplications that parse untrusted Markdown with `ENABLE_WIKILINKS` set,\nincluding through `Options::all()`, are affected. The option is off by default.\nParsing without it is not affected.\n\nThe flaw was fixed in\n[#1186](https://github.com/pulldown-cmark/pulldown-cmark/pull/1186) and\nreleased in 0.13.6.",
  "id": "RUSTSEC-2026-0433",
  "modified": "2026-11-02T11:17:24Z",
  "published": "2026-10-28T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/pulldown-cmark"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0433.html"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pulldown-cmark/pulldown-cmark/pull/1186"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pulldown-cmark/pulldown-cmark/pull/1186"
    }
  ],
  "related": [],
  "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": "Quadratic parsing of nested image wikilinks with `ENABLE_WIKILINKS`"
}



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