CVE-2026-59850

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libssh Channel Data Use-After-Free Vulnerability

Publication date: 2026-07-21

Last updated on: 2026-07-22

Assigner: Red Hat, Inc.

Description

A flaw was found in libssh. If data packets are processed after a channel is closed, channel data callbacks can be invoked after the associated data has already been freed, leading to crashes or possible use-after-free conditions.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-07-21

Last Modified

2026-07-22

Generated

2026-07-22

AI Q&A

2026-07-21

EPSS Evaluated

N/A

NVD

CVE-2026-59850

EUVD

EUVD-2026-46266

Affected Vendors & Products

Vendor	Product	Version / Range
libssh	libssh	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-416	The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Attack-Flow Graph

Executive Summary

This vulnerability is a use-after-free flaw in libssh. It occurs when data packets are processed after a channel is closed. Channel data callbacks may be invoked after the associated data has been freed, which can cause crashes or use-after-free conditions.

Detection Guidance

Detecting this vulnerability requires checking for crashes or use-after-free errors in applications using libssh, particularly those handling SFTP or channel data callbacks. Monitor system logs for segmentation faults or crashes in libssh-related processes. Use tools like AddressSanitizer (ASan) during compilation to detect memory corruption issues.

Impact Analysis

This vulnerability can impact applications using libssh, especially SFTP-backed ones. It may lead to crashes or arbitrary code execution if exploited, potentially compromising the security of systems relying on libssh for secure communications.

Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by enabling use-after-free conditions that may lead to crashes or memory corruption. Such issues might compromise data integrity or availability, which are critical under these regulations. However, the provided context does not explicitly link this flaw to specific compliance violations.

Mitigation Strategies

Update libssh to the latest patched version immediately. If updating is not possible, disable SFTP-backed applications or services using libssh until patched. Restrict network access to libssh services to trusted users only to reduce exposure.

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