Full Report
An error as small as a single flipped memory bit is all it takes to expose a private key.
Analysis Summary
# Vulnerability: Passive SSH Key Compromise via Computational Errors in RSA Signature Generation
## CVE Details
- CVE ID: Not explicitly provided in the text (Research paper exists: "[Passive SSH Key Compromise via Lattices](https://eprint.iacr.org/2023/1711.pdf)")
- CVSS Score: Not explicitly provided. (Severity is implied as **High** due to private key exposure).
- CWE: Implied relation to improper error handling/signature validation, possibly CWE-310 (Cryptographic Issues) or CWE-327 (Use of a Broken or Risky Cryptographic Algorithm/Implementation Flaw).
## Affected Systems
- Products: Systems using SSH for secure shell connections. Potentially IPsec connections as well.
- Versions: Implementations of SSH, including OpenSSH, that rely on the **RSA cryptographic algorithm** for signature generation initialization and lack robust countermeasures against signature faults.
- Configurations: Any configuration where naturally occurring computational errors (like a single flipped memory bit) occur during the RSA signature generation phase of connection establishment, and where existing countermeasures fail to detect the fault before the signature is sent.
## Vulnerability Description
This vulnerability arises from flaws in the implementation of RSA signature generation during the initial connection handshake of SSH (and potentially IPsec). When a natural computational error (e.g., a bit flip in memory/DRAM) occurs, it can lead to a single malformed RSA signature. If this faulty signature is observed passively by an adversary—without the need for active fault induction—the adversary can use the faulty signature alongside a valid signature to perform a Greatest Common Denominator (GCD) mathematical operation. This operation allows the attacker to derive one of the prime factors used to create the RSA private key, thus compromising the entire private key.
## Exploitation
- Status: **PoC available** (Research paper demonstrates successful key recovery from observed public Internet traffic from the last seven years).
- Complexity: **Low to Medium**. The passive method relies on waiting for naturally occurring errors, but the mathematical recovery from the observed signatures is highly effective once a faulty signature is captured.
- Attack Vector: **Network** (Passive observation of unsecured signature exchange data during connection negotiation).
## Impact
- Confidentiality: **High** (Complete compromise of the private key used for secure sessions).
- Integrity: **High** (Compromised key can be used to impersonate the server).
- Availability: **Low** (Direct impact is on key secrecy, not service availability, though service disruption could occur if keys are rotated).
## Remediation
### Patches
- Specific patch versions are not listed as this is a summary of research findings, not a vendor advisory. Users should consult vendor documentation for OpenSSH and other affected SSH/IPsec implementations for updates addressing mathematical result validation during signature generation.
### Workarounds
1. **Defensive Protocol Upgrade:** Implementations should adopt protections similar to those introduced in **TLS 1.3**, which specifically encrypts handshake messages, thus hiding the faulty signature (or the necessary data derived from it) from passive observation during negotiation.
2. **Ensure Countermeasures are Active:** Verify that existing countermeasures designed to check for signature faults **before** transmission are functioning with near-100% accuracy across all relevant cryptographic operations (RSA signature generation).
3. **Robustness Review:** Investigate potential sources of computational faults (e.g., software bugs, memory corruption, failing hardware/DRAM) and apply defense-in-depth mechanisms.
## Detection
- Indicators of compromise: A sudden increase in successful passive interception of RSA signatures during SSH connection setups, or unexpected private key compromise without corresponding active intrusion attempts.
- Detection methods and tools: Monitoring network traffic for unusual or potentially malformed RSA signature packets exchanged during SSH handshakes (though an attacker only needs to capture the final signature). Deep inspection tools focusing on cryptographic protocol layers might reveal faulty signatures if the signature is momentarily exposed before countermeasures execute.
## References
- Vendor advisories: None specified in the text, refer to the research paper's authors/institution for official confirmation.
- Relevant links - defanged:
- Research Paper: `eprint.iacr.org/2023/1711.pdf`
- Background on GCD Attack: `infoscience.epfl.ch/record/164524/files/nscan20.PDF`
- Background on GCD Attack: `link.springer.com/content/pdf/10.1007/s001450010016.pdf`
- Historical TLS Context: `redhat.com/en/blog/factoring-rsa-keys-tls-perfect-forward-secrecy`
- Previous Research: `usenix.org/system/files/sec22-sullivan.pdf`