How severe is CVE-2026-66032?

CVE-2026-66032 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-66032 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-66032?

CVE-2026-66032 affects Libssh2. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-66032?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-66032 published?

CVE-2026-66032 was published on 2026-07-24 and last updated on 2026-08-07.

CVE-2026-66032

CVE-2026-66032 is a high-severity vulnerability in Libssh2 with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-415.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v4: 8.7
EPSS exploit prediction: 0% (20th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-415
Affected product: Libssh2
Published: 2026-07-24
Last modified: 2026-08-07

Description

libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open() function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.

Frequently asked questions

What is CVE-2026-66032?: libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open() function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.
How severe is CVE-2026-66032?: CVE-2026-66032 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-66032 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-66032?: CVE-2026-66032 affects Libssh2. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-66032?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-66032 published?: CVE-2026-66032 was published on 2026-07-24 and last updated on 2026-08-07.

References

Affected products (1)

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

More vulnerabilities in Libssh2

CVE-2019-3859 — Critical (CVSS 9.1): An out of bounds read flaw was discovered in libssh2 before 1.8.1 in the _libssh2_packet_require and…
CVE-2019-3857 — High (CVSS 8.8): An integer overflow flaw which could lead to an out of bounds write was discovered in libssh2 before 1.8.1 in the way…
CVE-2019-3856 — High (CVSS 8.8): An integer overflow flaw, which could lead to an out of bounds write, was discovered in libssh2 before 1.8.1 in the way…
CVE-2019-3855 — High (CVSS 8.8): An integer overflow flaw which could lead to an out of bounds write was discovered in libssh2 before 1.8.1 in the way…
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CVE-2019-17498 — High (CVSS 8.1): In libssh2 v1.9.0 and earlier versions, the SSH_MSG_DISCONNECT logic in packet.c has an integer overflow in a bounds…

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Other CWE-415 (Double Free) vulnerabilities

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CVE-2026-52993 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: tipc: fix double-free in…
CVE-2020-37239 — Critical (CVSS 9.8): libbabl 0.1.62 contains a broken double free detection vulnerability that allows attackers to bypass memory safety…
CVE-2026-43414 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: scsi: qla2xxx: Completely fix fcport double…
CVE-2026-43011 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: net/x25: Fix potential double free of skb When…

Browse all CWE-415 (Double Free) vulnerabilities →