CVE-2019-11479
Publication date 17 June 2019
Last updated 24 July 2024
Ubuntu priority
Cvss 3 Severity Score
Jonathan Looney discovered that the Linux kernel default MSS is hard-coded to 48 bytes. This allows a remote peer to fragment TCP resend queues significantly more than if a larger MSS were enforced. A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commits 967c05aee439e6e5d7d805e195b3a20ef5c433d6 and 5f3e2bf008c2221478101ee72f5cb4654b9fc363.
From the Ubuntu Security Team
Jonathan Looney discovered that the Linux kernel could be coerced into segmenting responses into multiple TCP segments. A remote attacker could construct an ongoing sequence of requests to cause a denial of service.
Mitigation
This can be mitigated by dropping all packets which specify a too small MSS value. For example, to only allow MSS values of greater than 500 bytes, an iptables rule can be specified as: sudo iptables -A INPUT -p tcp -m tcpmss --mss 1:500 -j DROP Note: this will only take effect if the net.ipv4.tcp_mtu_probing sysctl is disabled as well.
Status
Package | Ubuntu Release | Status |
---|---|---|
linux | ||
18.04 LTS bionic |
Fixed 4.15.0-54.58
|
|
16.04 LTS xenial |
Fixed 4.4.0-154.181
|
|
14.04 LTS trusty | Ignored | |
linux-aws | ||
18.04 LTS bionic |
Fixed 4.15.0-1043.45
|
|
16.04 LTS xenial |
Fixed 4.4.0-1087.98
|
|
14.04 LTS trusty |
Fixed 4.4.0-1048.52
|
|
linux-aws-hwe | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial |
Fixed 4.15.0-1043.45~16.04.1
|
|
14.04 LTS trusty | Not in release | |
linux-azure | ||
18.04 LTS bionic |
Fixed 4.18.0-1023.24~18.04.1
|
|
16.04 LTS xenial |
Fixed 4.15.0-1049.54
|
|
14.04 LTS trusty |
Fixed 4.15.0-1049.54~14.04.1
|
|
linux-azure-edge | ||
18.04 LTS bionic |
Fixed 4.18.0-1023.24~18.04.1
|
|
16.04 LTS xenial |
Fixed 4.15.0-1049.54
|
|
14.04 LTS trusty | Not in release | |
linux-euclid | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Ignored | |
14.04 LTS trusty | Not in release | |
linux-flo | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Ignored | |
14.04 LTS trusty | Not in release | |
linux-gcp | ||
18.04 LTS bionic |
Fixed 4.15.0-1036.38
|
|
16.04 LTS xenial |
Fixed 4.15.0-1036.38~16.04.1
|
|
14.04 LTS trusty | Not in release | |
linux-gcp-edge | ||
18.04 LTS bionic |
Fixed 4.18.0-1015.16~18.04.1
|
|
16.04 LTS xenial | Not in release | |
14.04 LTS trusty | Not in release | |
linux-gke | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Ignored | |
14.04 LTS trusty | Not in release | |
linux-gke-4.15 | ||
18.04 LTS bionic |
Fixed 4.15.0-1036.38
|
|
16.04 LTS xenial | Not in release | |
14.04 LTS trusty | Not in release | |
linux-gke-5.0 | ||
18.04 LTS bionic |
Not affected
|
|
16.04 LTS xenial | Not in release | |
14.04 LTS trusty | Not in release | |
linux-goldfish | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Ignored | |
14.04 LTS trusty | Not in release | |
linux-grouper | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Not in release | |
14.04 LTS trusty | Not in release | |
linux-hwe | ||
18.04 LTS bionic |
Fixed 4.18.0-25.26~18.04.1
|
|
16.04 LTS xenial |
Fixed 4.15.0-54.58~16.04.1
|
|
14.04 LTS trusty | Not in release | |
linux-hwe-edge | ||
18.04 LTS bionic |
Fixed 5.0.0-20.21~18.04.1
|
|
16.04 LTS xenial |
Fixed 4.15.0-54.58~16.04.1
|
|
14.04 LTS trusty | Not in release | |
linux-kvm | ||
18.04 LTS bionic |
Fixed 4.15.0-1038.38
|
|
16.04 LTS xenial |
Fixed 4.4.0-1051.58
|
|
14.04 LTS trusty | Not in release | |
linux-lts-trusty | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Not in release | |
14.04 LTS trusty | Not in release | |
linux-lts-utopic | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Not in release | |
14.04 LTS trusty | Not in release | |
linux-lts-vivid | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Not in release | |
14.04 LTS trusty | Not in release | |
linux-lts-wily | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Not in release | |
14.04 LTS trusty | Not in release | |
linux-lts-xenial | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Not in release | |
14.04 LTS trusty |
Fixed 4.4.0-154.181~14.04.1
|
|
linux-maguro | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Not in release | |
14.04 LTS trusty | Not in release | |
linux-mako | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Ignored | |
14.04 LTS trusty | Not in release | |
linux-manta | ||
18.04 LTS bionic | Not in release | |
16.04 LTS xenial | Not in release | |
14.04 LTS trusty | Not in release | |
linux-oem | ||
18.04 LTS bionic |
Fixed 4.15.0-1045.50
|
|
16.04 LTS xenial | Ignored | |
14.04 LTS trusty | Not in release | |
linux-oracle | ||
18.04 LTS bionic |
Fixed 4.15.0-1017.19
|
|
16.04 LTS xenial |
Fixed 4.15.0-1017.19~16.04.2
|
|
14.04 LTS trusty | Not in release | |
linux-raspi2 | ||
18.04 LTS bionic |
Fixed 4.15.0-1040.43
|
|
16.04 LTS xenial |
Fixed 4.4.0-1114.123
|
|
14.04 LTS trusty | Not in release | |
linux-snapdragon | ||
18.04 LTS bionic |
Fixed 4.15.0-1057.62
|
|
16.04 LTS xenial |
Fixed 4.4.0-1118.124
|
|
14.04 LTS trusty | Not in release |
Get expanded security coverage with Ubuntu Pro
Reduce your average CVE exposure time from 98 days to 1 day with expanded CVE patching, ten-years security maintenance and optional support for the full stack of open-source applications. Free for personal use.
Get Ubuntu ProNotes
tyhicks
This issue is primarily due to the TCP spec not defining a minimum value for the Minimum Segment Size (MSS). The Linux kernel cannot safely put a restriction on the MSS because it may break valid TCP connections. This issue will be addressed by allowing a system administrator to raise the smallest acceptable MSS value but there will be no default mitigation by default.
Patch details
Package | Patch details |
---|---|
linux |
Severity score breakdown
Parameter | Value |
---|---|
Base score | 7.5 · High |
Attack vector | Network |
Attack complexity | Low |
Privileges required | None |
User interaction | None |
Scope | Unchanged |
Confidentiality | None |
Integrity impact | None |
Availability impact | High |
Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
References
Related Ubuntu Security Notices (USN)
- USN-4041-1
- Linux kernel update
- 29 June 2019
- USN-4041-2
- Linux kernel (HWE) update
- 29 June 2019