Command injection via incomplete username filtering
Published Jul 21, 2026 · Updated Jul 21, 2026
Command injection in libssh ProxyCommand handling allows local users to expose environment variables through a crafted SSH username. The ssh_check_username_syntax() path in src/misc.c uses an incomplete dangerous-character filter, letting shell-significant username bytes reach shell-evaluated ProxyCommand expansion. Exploitation requires a client to combine untrusted username input with ProxyCommand execution and user interaction; effects are limited to the invoking user's shell context.
Summary
What happened
Command injection in libssh ProxyCommand handling allows local users to expose environment variables through a crafted SSH username. The ssh_check_username_syntax() path in src/misc.c uses an incomplete dangerous-character filter, letting shell-significant username bytes reach shell-evaluated ProxyCommand expansion. Exploitation requires a client to combine untrusted username input with ProxyCommand execution and user interaction; effects are limited to the invoking user's shell context.
The record
- CVE
- CVE-2026-59846
- Published
- Jul 21, 2026
- Updated
- Jul 21, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat Enterprise Linux 10
- Classifications
- CWE-78, T1059.004
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 21, 2026CVE publishedPublication date reported by the CVE source.
- Jul 21, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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