The openssl gem for Ruby uses the same initialization vector (IV) in GCM Mode (aes-*-gcm) when the IV is set before the key, which makes it easier for context-dependent attackers to bypass the encryption protection mechanism.
The MITRE CVE dictionary describes this issue as:
Find out more about CVE-2016-7798 from the MITRE CVE dictionary dictionary and NIST NVD.
NOTE: The following CVSS v2 metrics and score provided are preliminary and subject to review.
| Base Score | 4.3 |
|---|---|
| Base Metrics | AV:N/AC:M/Au:N/C:P/I:N/A:N |
| Access Vector | Network |
| Access Complexity | Medium |
| Authentication | None |
| Confidentiality Impact | Partial |
| Integrity Impact | None |
| Availability Impact | None |
NOTE: The following CVSS v3 metrics and score provided are preliminary and subject to review.
| CVSS3 Base Score | 3.7 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N |
| Attack Vector | Network |
| Attack Complexity | High |
| Privileges Required | None |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality | Low |
| Integrity Impact | None |
| Availability Impact | None |
Find out more about Red Hat support for the Common Vulnerability Scoring System (CVSS).
| Platform | Package | State |
|---|---|---|
| Red Hat Software Collections for Red Hat Enterprise Linux | rh-ruby23-ruby | Will not fix |
| Red Hat Software Collections for Red Hat Enterprise Linux | ruby200-ruby | Will not fix |
| Red Hat Software Collections for Red Hat Enterprise Linux | rh-ruby22-ruby | Will not fix |
| Red Hat Enterprise Linux 7 | ruby | Will not fix |
| Red Hat Enterprise Linux 6 | ruby | Will not fix |
| Red Hat Enterprise Linux 5 | ruby | Will not fix |
A possible workaround to this flaw is, when using aes-256-gcm mode, always set the key first and then the iv. For example when setting random keys and iv use the following code segment:
key = cipher.random_key
iv = cipher.random_iv
Vulmon