CVE-2026-55586

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Source
https://cve.org/CVERecord?id=CVE-2026-55586
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55586.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-55586
Aliases
  • GHSA-m423-rp8p-whj8
Published
2026-08-20T16:35:07Z
Modified
2026-08-24T03:59:15Z
Severity
  • 6.6 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:L CVSS Calculator
Summary
SumatraPDF: Heap out-of-bounds write in vendored CHMLib LZX Huffman table construction reachable from crafted CHM files
Details

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.

Database specific 
{
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
        "CWE-119",
        "CWE-787"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55586.json"
}
References

Affected packages

Git / github.com/sumatrapdfreader/sumatrapdf

Affected ranges

Type
GIT
Repo
https://github.com/sumatrapdfreader/sumatrapdf
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
13b3d4204dd12d93d426f2157b157b149edc29bf
Database specific
Show details 
{
    "extracted_events": [
        {
            "introduced": "0"
        },
        {
            "last_affected": "3.6.1rel"
        }
    ],
    "source": [
        "AFFECTED_FIELD",
        "REFERENCES"
    ]
}

Affected versions

1.*
1.4split
1.5split
1.6split
1.7split
1.8split
1.9split
2.*
2.0split
2.1split
2.2split
2.3split
2.4split
2.5split
3.*
3.0split
3.1.2rel
3.2

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55586.json"
vanir_signatures 
[
    {
        "deprecated": false,
        "digest": {
            "function_hash": "333466651800751386784968678698376194028",
            "length": 1150
        },
        "id": "CVE-2026-55586-33d90d36",
        "signature_type": "Function",
        "signature_version": "v1",
        "source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf",
        "target": {
            "file": "ext/CHMLib/lzx.c",
            "function": "make_decode_table"
        }
    },
    {
        "deprecated": false,
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                "3503848909521385358248225449473124758",
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            ],
            "threshold": 0.9
        },
        "id": "CVE-2026-55586-3bf1f236",
        "signature_type": "Line",
        "signature_version": "v1",
        "source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf",
        "target": {
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        }
    },
    {
        "deprecated": false,
        "digest": {
            "function_hash": "178801226923716997501815782287108463511",
            "length": 900
        },
        "id": "CVE-2026-55586-440c2380",
        "signature_type": "Function",
        "signature_version": "v1",
        "source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf",
        "target": {
            "file": "src/Flags.cpp",
            "function": "Flags::~Flags"
        }
    },
    {
        "deprecated": false,
        "digest": {
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            ],
            "threshold": 0.9
        },
        "id": "CVE-2026-55586-4d9b57bc",
        "signature_type": "Line",
        "signature_version": "v1",
        "source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf",
        "target": {
            "file": "src/SumatraStartup.cpp"
        }
    },
    {
        "deprecated": false,
        "digest": {
            "function_hash": "260278129576066028231647026994909904072",
            "length": 9622
        },
        "id": "CVE-2026-55586-5dfdca3c",
        "signature_type": "Function",
        "signature_version": "v1",
        "source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf",
        "target": {
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            "function": "ParseFlags"
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    },
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                "271702138280848840092882818818405534006"
            ],
            "threshold": 0.9
        },
        "id": "CVE-2026-55586-76802e3d",
        "signature_type": "Line",
        "signature_version": "v1",
        "source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf",
        "target": {
            "file": "ext/CHMLib/lzx.h"
        }
    },
    {
        "deprecated": false,
        "digest": {
            "function_hash": "907585046289940280678462613265219312",
            "length": 11541
        },
        "id": "CVE-2026-55586-8f01f058",
        "signature_type": "Function",
        "signature_version": "v1",
        "source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf",
        "target": {
            "file": "src/SumatraStartup.cpp",
            "function": "WinMain"
        }
    },
    {
        "deprecated": false,
        "digest": {
            "line_hashes": [
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                "222847510846130793673140604401394174680",
                "186603889605839057154204174214355175907"
            ],
            "threshold": 0.9
        },
        "id": "CVE-2026-55586-a711dc4a",
        "signature_type": "Line",
        "signature_version": "v1",
        "source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf",
        "target": {
            "file": "src/Flags.h"
        }
    },
    {
        "deprecated": false,
        "digest": {
            "line_hashes": [
                "224328496414094476845108136837497340834",
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            ],
            "threshold": 0.9
        },
        "id": "CVE-2026-55586-d735e0fa",
        "signature_type": "Line",
        "signature_version": "v1",
        "source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/13b3d4204dd12d93d426f2157b157b149edc29bf",
        "target": {
            "file": "ext/CHMLib/lzx.c"
        }
    }
]
vanir_signatures_modified 
"2026-08-24T03:59:15Z"