SSH plaintext modification via ignored AES-GCM tag failure
Published Jul 21, 2026 · Updated Jul 21, 2026
Cryptographic verification failure in libssh on affected Red Hat products allows man-in-the-middle attackers to alter SSH plaintext. In src/libcrypto.c, the OpenSSL decrypt path checks EVP_DecryptFinal incorrectly and fails to treat an invalid AES-GCM authentication tag as an integrity error. Exploitation requires an affected OpenSSL-backed build, negotiation of an AES-GCM cipher, and an in-path network position; the established consequence is undetected plaintext modification.
Summary
What happened
Cryptographic verification failure in libssh on affected Red Hat products allows man-in-the-middle attackers to alter SSH plaintext. In src/libcrypto.c, the OpenSSL decrypt path checks EVP_DecryptFinal incorrectly and fails to treat an invalid AES-GCM authentication tag as an integrity error. Exploitation requires an affected OpenSSL-backed build, negotiation of an AES-GCM cipher, and an in-path network position; the established consequence is undetected plaintext modification.
The record
- CVE
- CVE-2026-59847
- Published
- Jul 21, 2026
- Updated
- Jul 21, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat Enterprise Linux 10
- Classifications
- CWE-253, CWE-1310, T1557
- Attack vector
- network
- Privileges
- unauthenticated
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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