CVE-2025-15661

libssh2 through 1.11.1, fixed in commit 2dae302, contains an out-of-bounds heap read vulnerability in the sftp_symlink() function in src/sftp.c that allows a malicious SSH server or man-in-the-middle attacker to disclose heap memory contents or cause a crash by sending a crafted SSH_FXP_NAME response. Attackers can supply a link_len value larger than the actual packet data in SSH_FXP_NAME responses for SFTP READLINK and REALPATH operations, triggering a heap buffer over-read of up to target_len minus one bytes due to the missing validation of available packet buffer size before the memcpy operation.

CVSS v3 6.5 MEDIUM

6.5^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.2 / Impact : 4.2

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/libssh2/libssh2/commit/2dae3024897e1898d389835151f4e9606227721d	Patch
https://github.com/libssh2/libssh2/pull/1705	Patch
https://github.com/libssh2/libssh2/pull/1717	Patch
https://www.vulncheck.com/advisories/libssh2-heap-buffer-over-read-via-sftp-symlink-in-sftp-c	Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-06-18 21:16

Updated : 2026-07-14 23:17

NVD link : CVE-2025-15661

Mitre link : CVE-2025-15661

CVE.ORG link : CVE-2025-15661

JSON object : View

Products Affected

libssh2

libssh2

CWE

CWE-125

Out-of-bounds Read

{"id": "CVE-2025-15661", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2025-15661", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-06-22T18:07:05.411976Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "disclosure@vulncheck.com", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 6.5, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "LOW"}, "impactScore": 4.2, "exploitabilityScore": 2.2}, {"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 6.5, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "LOW"}, "impactScore": 4.2, "exploitabilityScore": 2.2}], "cvssMetricV40": [{"type": "Secondary", "source": "disclosure@vulncheck.com", "cvssData": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 8.3, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "HIGH", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/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", "exploitMaturity": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "userInteraction": "NONE", "attackComplexity": "HIGH", "attackRequirements": "NONE", "privilegesRequired": "NONE", "subIntegrityImpact": "NONE", "vulnIntegrityImpact": "NONE", "integrityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "availabilityRequirement": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "subConfidentialityImpact": "NONE", "vulnConfidentialityImpact": "LOW", "confidentialityRequirement": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED"}}]}, "affected": [{"source": "disclosure@vulncheck.com", "affectedData": [{"repo": "https://github.com/libssh2/libssh2", "vendor": "libssh2", "product": "libssh2", "versions": [{"status": "affected", "version": "0", "versionType": "semver", "lessThanOrEqual": "1.11.1"}, {"status": "unaffected", "version": "2dae3024897e1898d389835151f4e9606227721d", "versionType": "git"}], "packageURL": "pkg:github/libssh2/libssh2", "defaultStatus": "affected"}]}], "published": "2026-06-18T21:16:27.143", "references": [{"url": "https://github.com/libssh2/libssh2/commit/2dae3024897e1898d389835151f4e9606227721d", "tags": ["Patch"], "source": "disclosure@vulncheck.com"}, {"url": "https://github.com/libssh2/libssh2/pull/1705", "tags": ["Patch"], "source": "disclosure@vulncheck.com"}, {"url": "https://github.com/libssh2/libssh2/pull/1717", "tags": ["Patch"], "source": "disclosure@vulncheck.com"}, {"url": "https://www.vulncheck.com/advisories/libssh2-heap-buffer-over-read-via-sftp-symlink-in-sftp-c", "tags": ["Third Party Advisory"], "source": "disclosure@vulncheck.com"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "disclosure@vulncheck.com", "description": [{"lang": "en", "value": "CWE-125"}]}], "descriptions": [{"lang": "en", "value": "libssh2 through 1.11.1, fixed in commit 2dae302, contains an out-of-bounds heap read vulnerability in the sftp_symlink() function in src/sftp.c that allows a malicious SSH server or man-in-the-middle attacker to disclose heap memory contents or cause a crash by sending a crafted SSH_FXP_NAME response. Attackers can supply a link_len value larger than the actual packet data in SSH_FXP_NAME responses for SFTP READLINK and REALPATH operations, triggering a heap buffer over-read of up to target_len minus one bytes due to the missing validation of available packet buffer size before the memcpy operation."}], "lastModified": "2026-07-14T23:17:19.207", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "00D62356-F677-41CF-AC66-2871AD2112BA", "versionEndIncluding": "1.11.1"}], "operator": "OR"}]}], "sourceIdentifier": "disclosure@vulncheck.com"}