{
  "document": {
    "category": "csaf_vex",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Public",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en-US",
    "notes": [
      {
        "category": "general",
        "text": "To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle",
        "title": "Additional Resources"
      },
      {
        "category": "legal_disclaimer",
        "text": "The information provided in the Microsoft Knowledge Base is provided \\\"as is\\\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.",
        "title": "Disclaimer"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "secure@microsoft.com",
      "name": "Microsoft Security Response Center",
      "namespace": "https://msrc.microsoft.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "CVE-2026-35201 Discount has an Out-of-bounds Read in rdiscount - VEX",
        "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-35201.json"
      },
      {
        "category": "external",
        "summary": "Microsoft Support Lifecycle",
        "url": "https://support.microsoft.com/lifecycle"
      },
      {
        "category": "external",
        "summary": "Common Vulnerability Scoring System",
        "url": "https://www.first.org/cvss"
      }
    ],
    "title": "Discount has an Out-of-bounds Read in rdiscount",
    "tracking": {
      "current_release_date": "2026-04-15T01:05:07.000Z",
      "generator": {
        "date": "2026-04-15T07:32:45.911Z",
        "engine": {
          "name": "MSRC Generator",
          "version": "1.0"
        }
      },
      "id": "msrc_CVE-2026-35201",
      "initial_release_date": "2026-04-02T00:00:00.000Z",
      "revision_history": [
        {
          "date": "2026-04-15T01:05:07.000Z",
          "legacy_version": "1",
          "number": "1",
          "summary": "Information published."
        }
      ],
      "status": "final",
      "version": "1"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_version",
                "name": "2.0",
                "product": {
                  "name": "CBL Mariner 2.0",
                  "product_id": "17086"
                }
              },
              {
                "category": "product_version",
                "name": "3.0",
                "product": {
                  "name": "Azure Linux 3.0",
                  "product_id": "17084"
                }
              }
            ],
            "category": "product_name",
            "name": "Azure Linux"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "cbl2 rubygem-rdiscount 2.2.0.2-3",
                "product": {
                  "name": "cbl2 rubygem-rdiscount 2.2.0.2-3",
                  "product_id": "1"
                }
              },
              {
                "category": "product_version_range",
                "name": "azl3 rubygem-rdiscount 2.2.7.1-1",
                "product": {
                  "name": "azl3 rubygem-rdiscount 2.2.7.1-1",
                  "product_id": "2"
                }
              }
            ],
            "category": "product_name",
            "name": "rubygem-rdiscount"
          }
        ],
        "category": "vendor",
        "name": "Microsoft"
      }
    ],
    "relationships": [
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "cbl2 rubygem-rdiscount 2.2.0.2-3 as a component of CBL Mariner 2.0",
          "product_id": "17086-1"
        },
        "product_reference": "1",
        "relates_to_product_reference": "17086"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "azl3 rubygem-rdiscount 2.2.7.1-1 as a component of Azure Linux 3.0",
          "product_id": "17084-2"
        },
        "product_reference": "2",
        "relates_to_product_reference": "17084"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-35201",
      "cwe": {
        "id": "CWE-125",
        "name": "Out-of-bounds Read"
      },
      "notes": [
        {
          "category": "general",
          "text": "GitHub_M",
          "title": "Assigning CNA"
        }
      ],
      "product_status": {
        "known_affected": [
          "17086-1",
          "17084-2"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-35201 Discount has an Out-of-bounds Read in rdiscount - VEX",
          "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-35201.json"
        }
      ],
      "remediations": [
        {
          "category": "none_available",
          "date": "2026-04-15T01:05:07.000Z",
          "details": "There is no fix available for this vulnerability as of now",
          "product_ids": [
            "17086-1"
          ]
        },
        {
          "category": "none_available",
          "date": "2026-04-15T01:05:07.000Z",
          "details": "There is no fix available for this vulnerability as of now",
          "product_ids": [
            "17084-2"
          ]
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 5.9,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "environmentalsScore": 0.0,
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "temporalScore": 5.9,
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "products": [
            "17086-1",
            "17084-2"
          ]
        }
      ],
      "title": "Discount has an Out-of-bounds Read in rdiscount"
    }
  ]
}

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:dafoster:rdiscount:*:*:*:*:*:ruby:*:*",
              "matchCriteriaId": "CD92C2DB-DEF1-4154-A725-76F41B1A0BBC",
              "versionEndExcluding": "2.2.7.4",
              "versionStartIncluding": "1.3.1.1",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Discount is an implementation of John Gruber\u0027s Markdown markup language in C. From 1.3.1.1 to before 2.2.7.4, a signed length truncation bug causes an out-of-bounds read in the default Markdown parse path. Inputs larger than INT_MAX are truncated to a signed int before entering the native parser, allowing the parser to read past the end of the supplied buffer and crash the process. This vulnerability is fixed in 2.2.7.4."
    }
  ],
  "id": "CVE-2026-35201",
  "lastModified": "2026-04-16T04:20:29.057",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 5.9,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-04-06T20:16:27.893",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Vendor Advisory",
        "Exploit"
      ],
      "url": "https://github.com/davidfstr/rdiscount/security/advisories/GHSA-6r34-94wq-jhrc"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-125"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "RubyGems",
        "name": "rdiscount"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.3.1.1"
            },
            {
              "fixed": "2.2.7.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-35201"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-125"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-06T17:53:59Z",
    "nvd_published_at": "2026-04-06T20:16:27Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nA signed length truncation bug causes an out-of-bounds read in the default Markdown parse path. Inputs larger than `INT_MAX` are truncated to a signed `int` before entering the native parser, allowing the parser to read past the end of the supplied buffer and crash the process\n\n### Details\n\nIn both public entry points:\n\n- `ext/rdiscount.c:97`\n- `ext/rdiscount.c:136`\n\n`RSTRING_LEN(text)` is passed directly into `mkd_string()`:\n\n```c\nMMIOT *doc = mkd_string(RSTRING_PTR(text), RSTRING_LEN(text), flags);\n```\n\n`mkd_string()` accepts `int len`:\n\n- `ext/mkdio.c:174`\n\n```c\nDocument * mkd_string(const char *buf, int len, mkd_flag_t flags)\n{\n    struct string_stream about;\n\n    about.data = buf;\n    about.size = len;\n\n    return populate((getc_func)__mkd_io_strget, \u0026about, flags \u0026 INPUT_MASK);\n}\n```\n\nThe parser stores the remaining input length in a signed `int`:\n\n- `ext/markdown.h:205`\n\n```c\nstruct string_stream {\n    const char *data;\n    int   size;\n};\n```\n\nThe read loop stops only when `size == 0`:\n\n- `ext/mkdio.c:161`\n\n```c\nint __mkd_io_strget(struct string_stream *in)\n{\n    if ( !in-\u003esize ) return EOF;\n\n    --(in-\u003esize);\n\n    return *(in-\u003edata)++;\n}\n```\n\nIf the Ruby string length exceeds `INT_MAX`, the value can truncate to a negative `int`. In that state, the parser continues incrementing `data` and reading past the end of the original Ruby string, causing an out-of-bounds read and native crash.\n\nAffected APIs:\n\n- `RDiscount.new(input).to_html`\n- `RDiscount.new(input).toc_content`\n\n### PoC\n\nCrash via `to_html`:\n\n```sh\nRUBYLIB=lib:ext ruby -e \u0027require \"rdiscount\"; n=2_200_000_000; s = \"a\" * n; warn \"built=#{s.bytesize}\"; RDiscount.new(s).to_html\"\u0027\n```\nresult:\n\n- `built=2200000000`\n- Ruby terminates with `[BUG] Segmentation fault`\n- top control frame: `CFUNC :to_html`\n\nsame result with `toc_content`\n\n### Impact\n\nThis is an out-of-bounds read with the main issue being reliable denial-of-service. Impacted is limited to deployments parses attacker-controlled Markdown and permits multi-GB inputs.\n\n### Fix\n\njust add a checked length guard before the `mkd_string()` call in both public entry points:\n\n- `ext/rdiscount.c:97`\n- `ext/rdiscount.c:136`\nex: \n```c\nVALUE text = rb_funcall(self, rb_intern(\"text\"), 0);\nlong text_len = RSTRING_LEN(text);\nVALUE buf = rb_str_buf_new(1024);\nCheck_Type(text, T_STRING);\n\nif (text_len \u003e INT_MAX) {\n    rb_raise(rb_eArgError, \"markdown input too large\");\n}\n\nMMIOT *doc = mkd_string(RSTRING_PTR(text), (int)text_len, flags);\n```\n\nThe same guard should be applied in `rb_rdiscount_toc_content()` before its `mkd_string()` call.",
  "id": "GHSA-6r34-94wq-jhrc",
  "modified": "2026-04-06T23:43:57Z",
  "published": "2026-04-06T17:53:59Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/davidfstr/rdiscount/security/advisories/GHSA-6r34-94wq-jhrc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-35201"
    },
    {
      "type": "WEB",
      "url": "https://github.com/davidfstr/rdiscount/commit/b1a16445e92e0d12c07594dedcdc56f80b317761"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/davidfstr/rdiscount"
    },
    {
      "type": "WEB",
      "url": "http://github.com/davidfstr/rdiscount/releases/tag/2.2.7.4"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "rdiscount has an Out-of-bounds Read"
}