# CVE-2026-66032: libssh2 Double-Free Heap Corruption via sftp_open()

> A malicious SSH server can trigger a double-free in libssh2's sftp_open function, leading to heap corruption and potential remote code execution on the client.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 24 Jul 2026
- **Updated:** 28 Jul 2026
- **Also known as:** ALPINE-CVE-2026-66032, AZL-93396, BELL-CVE-2026-66032, CLSA-2026-1786447189, CLSA-2026-1786478067, CLSA-2026-1786526353, CLSA-2026-1787063936, CLSA-2026-1787064509, CLSA-2026-1787393556, CLSA-2026-1787740667, DEBIAN-CVE-2026-66032, ECHO-416c-75e9-1367, GHSA-83r8-6c29-8gwr, JLSEC-2026-1085, ROOT-OS-DEBIAN-11-CVE-2026-66032, UBUNTU-CVE-2026-66032

## What is CVE-2026-66032?

CVE-2026-66032 is a high-severity use after free vulnerability in libssh2, published on 24 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2026-66032?

It affects 1 product.


Products: Libssh2 Libssh2.

## How do I fix CVE-2026-66032?

Apply the vendor's patch.

## Is CVE-2026-66032 being exploited?

There is no known exploitation of CVE-2026-66032 in the wild and no public exploit code.

## Other vulnerabilities in libssh2

- [CVE-2026-55200](https://insights.sbomify.com/CVE-2026-55200/): libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c (critical 9.2)
- [CVE-2026-66033](https://insights.sbomify.com/CVE-2026-66033/): libssh2 Integer Underflow DoS via AES-GCM Cipher Negotiation (high 8.7)
- [CVE-2026-58050](https://insights.sbomify.com/CVE-2026-58050/): libssh2 - Integer Overflow in publickey Subsystem Attribute Allocation (high 8.3)
- [CVE-2026-58051](https://insights.sbomify.com/CVE-2026-58051/): libssh2 - Free of Uninitialized Pointer in publickey List Cleanup (high 8.3)
- [CVE-2025-15661](https://insights.sbomify.com/CVE-2025-15661/): libssh2 - Heap Buffer Over-read via sftp_symlink() in sftp.c (high 8.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66032 and fix it if it is affected.

What it is: CVE-2026-66032 is a high-severity use after free vulnerability in libssh2, published on 24 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-66032 in the wild and no public exploit code.

Affected product: libssh2. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-66032/ (Markdown: https://insights.sbomify.com/CVE-2026-66032/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66032
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66032
- OSV: https://osv.dev/vulnerability/CVE-2026-66032

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66032/
Summaries are generated and may contain mistakes; the official description above is the record.