Memory exposure and crash via rekey length reuse
Published Aug 31, 2021 · Updated Aug 3, 2024
Heap-buffer overflow in libssh 0.9.1 through 0.9.5 allows remote authenticated users to read or write out of bounds during SSH rekeying. The key-exchange state reuses one length value for secret_hash and session_id after a new algorithm creates a digest of a different size. An authenticated SSH peer must request the mismatched rekey; the resulting access can expose adjacent memory or crash the linked process.
Summary
What happened
Heap-buffer overflow in libssh 0.9.1 through 0.9.5 allows remote authenticated users to read or write out of bounds during SSH rekeying. The key-exchange state reuses one length value for secret_hash and session_id after a new algorithm creates a digest of a different size. An authenticated SSH peer must request the mismatched rekey; the resulting access can expose adjacent memory or crash the linked process.
The record
- CVE
- CVE-2021-3634
- Published
- Aug 31, 2021
- Updated
- Aug 3, 2024
- Vendor
- libssh
- Product
- libssh
- Classifications
- CWE-787, T1499.004
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 31, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=libssh 0.9.6
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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