SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, ChmFile::GetCharZ() narrows file-controlled unsigned string offsets from /#WINDOWS and /#IVB to signed integers without a lower-bound check. An offset that becomes negative can make the function read before the /#STRINGS buffer, causing deterministic application termination. No broader impact is claimed beyond the advisory-supported conditions. No fixed version is available as of this review.
{
"cna_assigner": "GitHub_M",
"cwe_ids": [
"CWE-125"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107738.json"
}{
"extracted_events": [
{
"introduced": "0"
},
{
"last_affected": "3.6.1"
}
],
"source": [
"AFFECTED_FIELD",
"REFERENCES"
]
}
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-107738.json"
[
{
"deprecated": false,
"digest": {
"line_hashes": [
"300426981365801951799513052451881105245",
"44003461603035836753667947272880798217",
"191448402986654612790008150530317847510",
"180180430064954597980864822438408456421",
"146721603798329529223172946927666931111",
"165441435043455372111516623351820020634",
"94396864851667047463377388242734878832",
"251450456216546555062597820057147573120",
"22661630783992783968356480019813172758",
"211191342035911755034253341575008824875",
"128943154191505563207805769665393005696",
"1701251640089346248700938297385306289",
"279802294764128008045833890763108672347",
"241932673837966555736495986171706959117",
"158462343271890274731363222281517084689"
],
"threshold": 0.9
},
"id": "CVE-2026-107738-a40734dd",
"signature_type": "Line",
"signature_version": "v1",
"source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/62254ed6d781ceb5cd16489bb423e7f591cd72c4",
"target": {
"file": "src/ChmFile.cpp"
}
},
{
"deprecated": false,
"digest": {
"function_hash": "312024343921472359672318793875743238885",
"length": 386
},
"id": "CVE-2026-107738-c1b66f3c",
"signature_type": "Function",
"signature_version": "v1",
"source": "https://github.com/sumatrapdfreader/sumatrapdf/commit/62254ed6d781ceb5cd16489bb423e7f591cd72c4",
"target": {
"file": "src/ChmFile.cpp",
"function": "GetCharZ"
}
}
]
"2026-10-10T07:06:10Z"