CVE-2023-6918
Description
A flaw was found in the libssh implements abstract layer for message digest (MD) operations implemented by different supported crypto backends. The return values from these were not properly checked, which could cause low-memory situations failures, NULL dereferences, crashes, or usage of the uninitialized memory as an input for the KDF. In this case, non-matching keys will result in decryption/integrity failures, terminating the connection.
Statement
This vulnerability in the libssh abstract layer for message digest operations is deemed to have a low impact due to several mitigating factors. Primarily, the absence of proper checks on return values from supported crypto backends may lead to low-memory situations, failures, NULL dereferences, crashes, or the utilization of uninitialized memory in the Key Derivation Function (KDF). While these potential consequences could disrupt the system, their likelihood is considered low, contributing to the low impact classification.
The maintainers of libssh, in conjunction with Red Hat, have assigned a CVSS3.1 score of 3.7 to this vulnerability. While the score acknowledges the existence of a vulnerability, the assigned value falls within the lower range of the scale, indicating a relatively modest level of risk.
Moreover, the practical exploitability of this vulnerability is characterized as theoretical and highly unlikely to yield tangible results. The difficulty in successfully exploiting the flaw adds a layer of security, further diminishing the potential impact. While acknowledging the risk of non-matching keys leading to decryption/integrity failures and connection termination, the combination of the low likelihood of exploitation and the relatively lower severity score results in an overall assessment of low impact.
Mitigation
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.7 | 5.3 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | Low | Low | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Red Hat CVSS v3 Score Explanation
The libssh maintainers have assigned a score of 3.7, which is endorsed by Red Hat. The exploitability of this vulnerability is primarily theoretical and highly improbable to produce any tangible results.
The high attack complexity associated with the mentioned vulnerability in libssh arises from its predominantly theoretical exploitability and the low likelihood of yielding practical results. The low impact on Availability (A) suggests that while the flaw could potentially lead to issues such as low-memory situations, failures, or crashes, the overall effect on system availability is not deemed severe. The confidentiality aspect (C) is not explicitly mentioned in the provided statement but would be marked as "N/A" if the vulnerability does not significantly impact data confidentiality. And Integrity is None, indicates that the vulnerability is not expected to significantly compromise or impact the integrity of data.
Understanding the Weakness (CWE)
Availability,Integrity
Technical Impact: Unexpected State; DoS: Crash, Exit, or Restart
An unexpected return value could place the system in a state that could lead to a crash or other unintended behaviors.
Acknowledgements
Red Hat would like to thank Jack Weinstein (<mike.code.bb.h@gmail.com>) for reporting this issue.
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