CVE-2026-110926
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OpenSSH Compression-Related Information Leak Vulnerability

Publication date: 2026-10-15

Last updated on: 2026-10-15

Assigner: redhat-SADP

Description
A flaw was found in OpenSSH. When compression is negotiated, channels on the same connection share one LZ77 dictionary. A peer who can write on one channel can recover plaintext from another channel by chosen-plaintext lengths.

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Meta Information

Published
2026-10-15
Last Modified
2026-10-15
Generated
2026-10-19
AI Q&A
2026-10-15
EPSS Evaluated
2026-10-18
NVD
CVE-2026-110926
EUVD
EUVD-2026-101837

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
Red Hat Red Hat Hardened Images *

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-203 The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.

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Executive Summary

This vulnerability is in OpenSSH where compression negotiation allows shared LZ77 dictionaries between channels on the same connection. An attacker who can write to one channel can recover plaintext from another channel by analyzing chosen-plaintext lengths.

Detection Guidance

To detect this vulnerability, check if SSH compression is enabled on your system. The default OpenSSH client does not enable compression, so verify configurations in /etc/ssh/ssh_config or user-specific configs. Use commands like 'ssh -v -C user@host' to see if compression is negotiated during connection.

Impact Analysis

If compression is enabled, plaintext from one channel could leak to another channel on the same connection. The default OpenSSH client does not enable compression, so default connections are not affected. Application-level compression should be preferred over SSH compression.

Compliance Impact

This vulnerability primarily impacts confidentiality by allowing plaintext recovery from one channel via another on the same connection when compression is enabled. For GDPR, this could violate Article 32 requirements for data protection and integrity. HIPAA may be affected if protected health information is exposed through side-channel attacks. Compliance depends on whether encryption is properly configured and compression is disabled by default.

Mitigation Strategies

Disable SSH compression if enabled. Ensure the OpenSSH client and server configurations do not force compression. Prefer application-level compression over SSH compression. Monitor for updates from Red Hat or OpenSSH for patches addressing CVE-2026-110926.

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