Synology-SA-18:44 Linux kernel

Publish Time: 2018-08-15 13:17:16 UTC+8

Last Updated: 2021-04-14 08:43:39 UTC+8



CVE-2018-5391, a.k.a. FragmentSmack attack, allows remote attackers to conduct denial-of-service attacks via a susceptible version of Synology Diskstation Manager (DSM), SkyNAS or VS960HD.

SRM 1.1 is not affected as CVE-2018-5391 only affects Linux kernel 3.9 or above.

Affected Products

Product Severity Fixed Release Availability
DSM 6.2 Important Upgrade to 6.2.1-23824-1 or above.
DSM 6.1 Important Upgrade to 6.2.1-23824-1 or above.
DSM 5.2 Important Upgrade to 6.2.1-23824-1 or above.
SkyNAS Important Will not fix.
VS960HD Important Will not fix.
SRM 1.1 Not affected N/A


If you need immediate assistance, please contact Synology technical support via


  • CVE-2018-5391
    • Severity: Important
    • CVSS3 Base Score: 7.5
    • CVSS3 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
    • The Linux kernel, versions 3.9+, is vulnerable to a denial of service attack with low rates of specially modified packets targeting IP fragment re-assembly. An attacker may cause a denial of service condition by sending specially crafted IP fragments. Various vulnerabilities in IP fragmentation have been discovered and fixed over the years. The current vulnerability (CVE-2018-5391) became exploitable in the Linux kernel with the increase of the IP fragment reassembly queue size.



Revision Date Description
1 2018-08-15 Initial public release.
2 2019-12-17 Update for DSM 6.2, DSM 6.1 and DSM 5.2 are now available in Affected Products.
3 2021-04-14 Disclosed vulnerability details.