CVE-2026-35199

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Source
https://cve.org/CVERecord?id=CVE-2026-35199
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-35199.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-35199
Aliases
  • GHSA-rvj8-8h6x-hjmg
Published
2026-04-06T19:44:31.143Z
Modified
2026-07-27T09:24:28.263859Z
Severity
  • 6.1 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H CVSS Calculator
Summary
SymCrypt SymCryptXmssSign function - Heap overflow via 64->32-bit leaf-count truncation
Details

SymCrypt is the core cryptographic function library currently used by Windows. From 103.5.0 to before 103.11.0, The SymCryptXmssSign function passes a 64-bit leaf count value to a helper function that accepts a 32-bit parameter. For XMSS^MT parameter sets with total tree height >= 32 (which includes standard predefined parameters), this causes silent truncation to zero, resulting in a drastically undersized scratch buffer allocation followed by a heap buffer overflow during signature computation. Exploiting this issue would require an application using SymCrypt to perform an XMSS^MT signature using an attacker-controlled parameter set. It is uncommon for applications to allow the use of attacker-controlled parameter sets for signing, since signing is a private key operation, and private keys must be trusted by definition. Additionally, XMSS(^MT) signing should only be performed in a Hardware Security Module (HSM). XMSS(^MT) signing is provided in SymCrypt only for testing purposes. This is a general rule irrespective of this CVE; XMSS(^MT) and other stateful signature schemes are only cryptographically secure when it is guaranteed that the same state cannot be reused for two different signatures, which cannot be guaranteed by software alone. For this reason, XMSS(^MT) signing is also not FIPS approved when performed outside of an HSM. Fixed in version 103.11.0.

Database specific 
{
    "cna_assigner": "GitHub_M",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/35xxx/CVE-2026-35199.json",
    "cwe_ids": [
        "CWE-122"
    ]
}
References

Affected packages

Git / github.com/microsoft/symcrypt

Affected ranges

Type
GIT
Repo
https://github.com/microsoft/symcrypt
Events
Introduced
241eff30aa052bb121958373a4f59f775f87d143
Fixed
748c20f1fc486beca1a2679ed06492712cfdc950
Database specific 
{
    "extracted_events": [
        {
            "introduced": "103.5.0"
        },
        {
            "fixed": "103.11.0"
        }
    ],
    "cpe": "cpe:2.3:a:microsoft:symcrypt:*:*:*:*:*:*:*:*",
    "source": [
        "AFFECTED_FIELD",
        "CPE_RANGE"
    ]
}

Affected versions

v103.*
v103.10.0
v103.10.1
v103.10.2
v103.5.0
v103.5.1
v103.6.0
v103.7.0
v103.8.0
v103.8.1
v103.9.0
v103.9.1

Database specific

vanir_signatures 
[
    {
        "signature_version": "v1",
        "deprecated": false,
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "277665804818202098486726019291688766405",
                "61691349921780670130149809457462465857",
                "79627393922929305957980030398304475876",
                "178198573139358800016442041815084881687",
                "235200274621926765480541721990024752197",
                "292310565973597489608635021415431103505",
                "288339791789984801739571841925861792801",
                "162526044050116551084208970693535725067",
                "60744131536571936184942471119931697753",
                "125463133269833187309043642558443802709",
                "170141117620335681011975853496252276668"
            ]
        },
        "id": "CVE-2026-35199-1b0e798c",
        "signature_type": "Line",
        "source": "https://github.com/microsoft/symcrypt/commit/748c20f1fc486beca1a2679ed06492712cfdc950",
        "target": {
            "file": "unittest/lib/testHbs.cpp"
        }
    },
    {
        "signature_version": "v1",
        "deprecated": false,
        "digest": {
            "length": 82.0,
            "function_hash": "16770605928824227784517527267958895201"
        },
        "id": "CVE-2026-35199-51a1613b",
        "signature_type": "Function",
        "source": "https://github.com/microsoft/symcrypt/commit/748c20f1fc486beca1a2679ed06492712cfdc950",
        "target": {
            "function": "testXmss",
            "file": "unittest/lib/testHbs.cpp"
        }
    },
    {
        "signature_version": "v1",
        "deprecated": false,
        "digest": {
            "length": 172.0,
            "function_hash": "182188606705191473115248959425571131254"
        },
        "id": "CVE-2026-35199-92bc3140",
        "signature_type": "Function",
        "source": "https://github.com/microsoft/symcrypt/commit/748c20f1fc486beca1a2679ed06492712cfdc950",
        "target": {
            "function": "SymCryptHbsSizeofScratchBytesForIncrementalTreehash",
            "file": "lib/xmss.c"
        }
    },
    {
        "signature_version": "v1",
        "deprecated": false,
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "330698869928100559783113234021996448935",
                "231675677535918862062727754855873683307",
                "70038591090330148709584395284744150370",
                "151598833149150311662082782836658463952",
                "81308382151238445198749743535368132293",
                "198361860022282118736876593428747808142",
                "271192173652520693003185028785233672147",
                "254179586454258643650167455374677783509",
                "87105273516208202373993302421459508247",
                "222597179000272988525990007771430526097",
                "11305194627799605196601041782811636344",
                "273510763903608628121969212658584553421",
                "35770550156724555357315189384381946574",
                "176165169748014069258695276712645966204",
                "3289839263683966853059660216696841915",
                "330612008658541489596522518944659910126",
                "146136487910996417256390705202442150373",
                "58672016731645968162792849177966800112",
                "305689780475731546923061705225668439554",
                "215525161576776489987542996655723222989",
                "13185264448998485547327210179525436211",
                "168078371220034638127844423060735216337",
                "124638636583260529154867758711388380531",
                "14115989171266719471807857561771831008",
                "146136487910996417256390705202442150373",
                "58672016731645968162792849177966800112",
                "305689780475731546923061705225668439554",
                "234942787146814939609262017166889177764",
                "184692392654801179778623599786383056726",
                "28045694232053496113520077133425924617",
                "30212698493107495556200079368018878264"
            ]
        },
        "id": "CVE-2026-35199-b40b1d95",
        "signature_type": "Line",
        "source": "https://github.com/microsoft/symcrypt/commit/748c20f1fc486beca1a2679ed06492712cfdc950",
        "target": {
            "file": "lib/xmss.c"
        }
    },
    {
        "signature_version": "v1",
        "deprecated": false,
        "digest": {
            "length": 1169.0,
            "function_hash": "153743323119053323771059835060487924983"
        },
        "id": "CVE-2026-35199-c173d26a",
        "signature_type": "Function",
        "source": "https://github.com/microsoft/symcrypt/commit/748c20f1fc486beca1a2679ed06492712cfdc950",
        "target": {
            "function": "SymCryptXmssSetParams",
            "file": "lib/xmss.c"
        }
    },
    {
        "signature_version": "v1",
        "deprecated": false,
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "18186715024787768345916191060758038130",
                "247580261823549367430912797469440983436",
                "329404992221242913720487769782578716778",
                "120333198166257000793767461618305426991",
                "83205076859359300762079861202338740376"
            ]
        },
        "id": "CVE-2026-35199-ccbde253",
        "signature_type": "Line",
        "source": "https://github.com/microsoft/symcrypt/commit/748c20f1fc486beca1a2679ed06492712cfdc950",
        "target": {
            "file": "unittest/lib/testutil.cpp"
        }
    },
    {
        "signature_version": "v1",
        "deprecated": false,
        "digest": {
            "length": 100.0,
            "function_hash": "96086444928567685361969239800582648928"
        },
        "id": "CVE-2026-35199-e190ef73",
        "signature_type": "Function",
        "source": "https://github.com/microsoft/symcrypt/commit/748c20f1fc486beca1a2679ed06492712cfdc950",
        "target": {
            "function": "testUtil",
            "file": "unittest/lib/testutil.cpp"
        }
    }
]
vanir_signatures_modified 
"2026-07-27T09:24:28Z"
source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-35199.json"