FKIE_CVE-2026-55586

Vulnerability from fkie_nvd - Published: 2026-08-20 17:18 - Updated: 2026-08-20 17:18
Severity
6.6 (Medium) - CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:L
Summary
SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, a crafted CHM file can supply malformed LZX Huffman code lengths to make_decode_table in ext/CHMLib/lzx.c. In the long-code branch, the function writes new internal nodes through next_symbol before validating that the canonical Huffman table has overflowed. The PRETREE case can write beyond the 104-entry PRETREE_table into adjacent heap state in struct LZXstate when reached through chm_open, chm_retrieve_object, LZXdecompress, and BUILD_TABLE. This produces heap memory corruption in the parser process, while arbitrary code execution has not been demonstrated. No fixed version is available as of this review.
References
security-advisories@github.comhttps://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf
security-advisories@github.comhttps://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-m423-rp8p-whj8
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "sumatrapdf",
          "vendor": "sumatrapdfreader",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c= 3.6.1rel"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, a crafted CHM file can supply malformed LZX Huffman code lengths to make_decode_table in ext/CHMLib/lzx.c. In the long-code branch, the function writes new internal nodes through next_symbol before validating that the canonical Huffman table has overflowed. The PRETREE case can write beyond the 104-entry PRETREE_table into adjacent heap state in struct LZXstate when reached through chm_open, chm_retrieve_object, LZXdecompress, and BUILD_TABLE. This produces heap memory corruption in the parser process, while arbitrary code execution has not been demonstrated. No fixed version is available as of this review."
    }
  ],
  "id": "CVE-2026-55586",
  "lastModified": "2026-08-20T17:18:27.723",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "LOW",
          "baseScore": 6.6,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 4.7,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-20T17:18:27.723",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-m423-rp8p-whj8"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-119"
        },
        {
          "lang": "en",
          "value": "CWE-787"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}



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