An issue was discovered in the base64d function in the SMTP listener in Exim before 4.90.1. By sending a handcrafted message, a buffer overflow may happen. This can be used to execute code remotely.
The MITRE CVE dictionary describes this issue as:
Find out more about CVE-2018-6789 from the MITRE CVE dictionary dictionary and NIST NVD.
This issue affects the versions of Exim as shipped in Red Hat Enterprise Linux 5. Red Hat Enterprise Linux 5 is already in the Extended Life Phase of its life cycle and Exim is not on the list of components supported via Red Hat Enterprise Linux 5 Extended Life-cycle Support (ELS) add-on, therefore there's currently no plan to address this issue in Red Hat Enterprise Linux 5. For more information about Red Hat Enterprise Linux 5 life cycle and ELS add-on scope of support, see:
https://access.redhat.com/support/policy/updates/errata/#Extended_Life_Cycle_Phase
https://access.redhat.com/articles/2901071
The Exim mail server is not shipped in Red Hat Enterprise Linux 6 and 7.
NOTE: The following CVSS v3 metrics and score provided are preliminary and subject to review.
| CVSS3 Base Score | 8.1 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
| Attack Vector | Network |
| Attack Complexity | High |
| Privileges Required | None |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity Impact | High |
| Availability Impact | High |
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise Linux 5 | exim | Will not fix |
Vulmon