FKIE_CVE-2026-63091
Vulnerability from fkie_nvd - Published: 2026-07-20 15:16 - Updated: 2026-07-20 17:18
Severity
Summary
ProFTPD before 1.3.9c and 1.3.10rc3 contains a signed integer overflow vulnerability in the mod_sftp module's SCP size-record parser that allows authenticated low-privilege attackers to bypass ASLR by sending a crafted file size value of UINT64_MAX, which results in a negative off_t value. Attackers can exploit the subsequent conversion to uint32_t, causing an approximately 4 GB requested read length and forcing the server to read beyond the end of the SSH channel data and write overread process memory into the uploaded file. In tested configurations, the disclosed data contains libc, libcrypto, and PIE pointers sufficient to derive their randomized base addresses, thereby bypassing ASLR and enabling reliable exploitation of memory corruption vulnerabilities in the same process.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "affected",
"product": "proftpd",
"repo": "https://github.com/proftpd/proftpd",
"vendor": "proftpd",
"versions": [
{
"lessThan": "1.3.9c",
"status": "affected",
"version": "0",
"versionType": "custom"
},
{
"lessThan": "1.3.10rc3",
"status": "affected",
"version": "1.3.10rc1",
"versionType": "custom"
}
]
}
],
"source": "disclosure@vulncheck.com"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "ProFTPD before 1.3.9c and 1.3.10rc3 contains a signed integer overflow vulnerability in the mod_sftp module\u0027s SCP size-record parser that allows authenticated low-privilege attackers to bypass ASLR by sending a crafted file size value of UINT64_MAX, which results in a negative off_t value. Attackers can exploit the subsequent conversion to uint32_t, causing an approximately 4 GB requested read length and forcing the server to read beyond the end of the SSH channel data and write overread process memory into the uploaded file. In tested configurations, the disclosed data contains libc, libcrypto, and PIE pointers sufficient to derive their randomized base addresses, thereby bypassing ASLR and enabling reliable exploitation of memory corruption vulnerabilities in the same process."
}
],
"id": "CVE-2026-63091",
"lastModified": "2026-07-20T17:18:21.050",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 6.5,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"version": "3.1"
},
"exploitabilityScore": 2.8,
"impactScore": 3.6,
"source": "disclosure@vulncheck.com",
"type": "Secondary"
}
],
"cvssMetricV40": [
{
"cvssData": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"availabilityRequirement": "NOT_DEFINED",
"baseScore": 7.1,
"baseSeverity": "HIGH",
"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "LOW",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"source": "disclosure@vulncheck.com",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-63091",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-07-20T16:32:31.417303Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-07-20T15:16:45.363",
"references": [
{
"source": "disclosure@vulncheck.com",
"url": "https://github.com/proftpd/proftpd/blob/master/RELEASE_NOTES"
},
{
"source": "disclosure@vulncheck.com",
"url": "https://github.com/proftpd/proftpd/commit/b9b7dde1bcd74bc23366484d53856b67b8d6d95e"
},
{
"source": "disclosure@vulncheck.com",
"url": "https://github.com/proftpd/proftpd/pull/2201"
},
{
"source": "disclosure@vulncheck.com",
"url": "https://github.com/proftpd/proftpd/releases/tag/v1.3.10rc3-3"
},
{
"source": "disclosure@vulncheck.com",
"url": "https://github.com/proftpd/proftpd/releases/tag/v1.3.9c"
},
{
"source": "disclosure@vulncheck.com",
"url": "https://www.vulncheck.com/advisories/proftpd-mod-sftp-signed-integer-overflow-via-scp-size-record-parser"
}
],
"sourceIdentifier": "disclosure@vulncheck.com",
"vulnStatus": "Received",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-126"
},
{
"lang": "en",
"value": "CWE-190"
}
],
"source": "disclosure@vulncheck.com",
"type": "Secondary"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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