CVE-2023-26485

{
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          "version": "2.0.3",
          "timestamp": "2025-02-11T17:20:05.803675Z"
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          "vendor": "github",
          "product": "cmark-gfm",
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              "version": "< 0.29.0.gfm.10"
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  "published": "2023-03-31T23:15:07.250",
  "references": [
    {
      "url": "https://github.com/github/cmark-gfm/commit/07a66c9bc341f902878e37d7da8647d6ef150987",
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        "Patch"
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      "url": "https://github.com/github/cmark-gfm/security/advisories/GHSA-r8vr-c48j-fcc5",
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  "vulnStatus": "Modified",
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      "description": [
        {
          "lang": "en",
          "value": "CWE-400"
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          "value": "CWE-407"
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  "descriptions": [
    {
      "lang": "en",
      "value": "cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. A polynomial time complexity issue in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service. This CVE covers quadratic complexity issues when parsing text which leads with either large numbers of `_` characters. This issue has been addressed in version 0.29.0.gfm.10. Users are advised to upgrade. Users unable to upgrade should validate that their input comes from trusted sources.\n\n\n\n\n### Impact\n\nA polynomial time complexity issue in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service.\n\n### Proof of concept\n\n```\n$ ~/cmark-gfm$ python3 -c 'pad = \"_\" * 100000; print(pad + \".\" + pad, end=\"\")' | time ./build/src/cmark-gfm --to plaintext\n```\n\nIncreasing the number 10000 in the above commands causes the running time to increase quadratically.\n\n### Patches\n\nThis vulnerability have been patched in 0.29.0.gfm.10.\n\n### Note on cmark and cmark-gfm\n\nXXX: TBD\n\n[cmark-gfm](https://github.com/github/cmark-gfm) is a fork of [cmark](https://github.com/commonmark/cmark) that adds the GitHub Flavored Markdown extensions. The two codebases have diverged over time, but share a common core. These bugs affect both `cmark` and `cmark-gfm`. \n\n### Credit\n\nWe would like to thank @gravypod for reporting this vulnerability.\n\n### References\n\nhttps://en.wikipedia.org/wiki/Time_complexity\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n\n* Open an issue in [github/cmark-gfm](https://github.com/github/cmark-gfm)\n"
    }
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  "lastModified": "2026-06-17T05:43:26.410",
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