It was found that xorg-x11-server before 1.19.0 including uses memcmp() to check the received MIT cookie against a series of valid cookies. If the cookie is correct, it is allowed to attach to the Xorg session. Since most memcmp() implementations return after an invalid byte is seen, this causes a time difference between a valid and invalid byte, which could allow an efficient brute force attack.
The MITRE CVE dictionary describes this issue as:
Find out more about CVE-2017-2624 from the MITRE CVE dictionary dictionary and NIST NVD.
Red Hat Product Security has rated this issue as having Low security
impact. This issue is not currently planned to be addressed in future
updates. For additional information, refer to the Issue Severity
Classification: https://access.redhat.com/security/updates/classification/.
NOTE: The following CVSS v3 metrics and score provided are preliminary and subject to review.
| CVSS3 Base Score | 5.9 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N |
| Attack Vector | Local |
| Attack Complexity | High |
| Privileges Required | None |
| User Interaction | None |
| Scope | Changed |
| Confidentiality | High |
| Integrity Impact | None |
| Availability Impact | None |
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise Linux 7 | xorg-x11-server | Will not fix |
| Red Hat Enterprise Linux 6 | xorg-x11-server | Will not fix |
| Red Hat Enterprise Linux 5 | xorg-x11-server | Will not fix |
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