Description
The flow_dissector feature in the Linux kernel 4.3 through 5.x before 5.3.10 has a device tracking vulnerability, aka CID-55667441c84f. This occurs because the auto flowlabel of a UDP IPv6 packet relies on a 32-bit hashrnd value as a secret, and because jhash (instead of siphash) is used. The hashrnd value remains the same starting from boot time, and can be inferred by an attacker. This affects net/core/flow_dissector.c and related code.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | linux | 5.3.15-1 | — |
| Debian 13 | linux | 5.3.15-1 | — |
| Debian 12 | linux | 5.3.15-1 | — |
| Debian 8 | linux-4.9 | 4.9.210-1~deb8u1 | DLA-2114-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 24.04 LTS | linux-raspi-realtime | No fix yet | — |
| Ubuntu 22.04 LTS | linux-riscv +2 | No fix yet | — |
| Ubuntu 20.04 LTS | linux-gke +2 | No fix yet | — |
| Ubuntu 18.04 LTS | linux | 4.15.0-74.84 | — |
| Ubuntu 18.04 LTS | linux-aws | 4.15.0-1057.59 | — |
| Ubuntu 18.04 LTS | linux-aws-5.0 | 5.0.0-1023.26~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-azure | 5.0.0-1028.30~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-azure-5.3 | 5.3.0-1008.9~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-gcp | 5.0.0-1028.29~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-gcp-5.3 | 5.3.0-1009.10~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-gcp-edge +1 | No fix yet | — |
| Ubuntu 18.04 LTS | linux-gke-4.15 | 4.15.0-1050.53 | — |
| Ubuntu 18.04 LTS | linux-gke-5.0 | 5.0.0-1027.28~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-hwe | 5.3.0-26.28~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-hwe-edge | 5.3.0-24.26~18.04.2 | — |
| Ubuntu 18.04 LTS | linux-kvm | 4.15.0-1052.52 | — |
| Ubuntu 18.04 LTS | linux-oem | 4.15.0-1066.76 | — |
| Ubuntu 18.04 LTS | linux-oem-osp1 | 5.0.0-1033.38 | — |
| Ubuntu 18.04 LTS | linux-oracle | 4.15.0-1031.34 | — |
| Ubuntu 18.04 LTS | linux-oracle-5.0 | 5.0.0-1009.14~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-raspi2 | 4.15.0-1053.57 | — |
| Ubuntu 18.04 LTS | linux-snapdragon | 4.15.0-1070.77 | — |
| Ubuntu 16.04 LTS | linux | 4.4.0-170.199 | — |
| Ubuntu 16.04 LTS | linux-aws | 4.4.0-1099.110 | — |
| Ubuntu 16.04 LTS | linux-aws-hwe | 4.15.0-1057.59~16.04.1 | — |
| Ubuntu 16.04 LTS | linux-azure | 4.15.0-1066.71 | — |
| Ubuntu 16.04 LTS | linux-gcp | 4.15.0-1052.56 | — |
| Ubuntu 16.04 LTS | linux-hwe | 4.15.0-74.83~16.04.1 | — |
| Ubuntu 16.04 LTS | linux-hwe-edge | No fix yet | — |
| Ubuntu 16.04 LTS | linux-kvm | 4.4.0-1063.70 | — |
| Ubuntu 16.04 LTS | linux-oracle | 4.15.0-1031.34~16.04.1 | — |
| Ubuntu 16.04 LTS | linux-raspi2 | 4.4.0-1126.135 | — |
| Ubuntu 16.04 LTS | linux-snapdragon | 4.4.0-1130.138 | — |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro FIPS 18.04 LTS | linux-aws-fips +2 | No fix yet | — |
| Ubuntu Pro FIPS 16.04 LTS | linux-fips | No fix yet | — |
| Ubuntu Pro FIPS-updates 18.04 LTS | linux-aws-fips | 4.15.0-2018.18 | — |
| Ubuntu Pro FIPS-updates 18.04 LTS | linux-azure-fips | 4.15.0-2006.7 | — |
| Ubuntu Pro FIPS-updates 16.04 LTS | linux-fips | 4.4.0-1026.31 | — |
| Ubuntu Pro 14.04 LTS | linux-aws | 4.4.0-1059.63 | — |
| Ubuntu Pro 14.04 LTS | linux-azure | 4.15.0-1066.71~14.04.1 | — |
| Ubuntu Pro 14.04 LTS | linux-lts-xenial | 4.4.0-170.199~14.04.1 | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | kernel-rt +12 | 4.18.0-193.rt13.51.el8 | RHSA-2020:1567 |
| RHEL 8 | perf +26 | 4.18.0-193.el8 | RHSA-2020:1769 |
| RHEL 7 | kernel-rt +10 | 3.10.0-1160.11.1.rt56.1145.el7 | RHSA-2020:5441 |
| RHEL 7 | perf +18 | 3.10.0-1160.11.1.el7 | RHSA-2020:5437 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 7 | kernel-uek +8 | 4.14.35-1902.303.4.1.el7uek | ELSA-2020-5715 |
| Oracle Linux 7 | perf +12 | 3.10.0-1160.11.1.el7 | ELSA-2020-5715, ELSA-2020-5437 |
Advisories 7
- RHSA-2020:1769 Red Hat Security Advisory: kernel security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Aug 22, 2026
- RHSA-2020:1567 Red Hat Security Advisory: kernel-rt security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2020:5441 Red Hat Security Advisory: kernel-rt security and bug fix update Red Hat Security Advisories (RHSA) · Jun 29, 2026
- RHSA-2020:5437 Red Hat Security Advisory: kernel security and bug fix update Red Hat Security Advisories (RHSA) · Jun 29, 2026
- DLA-2114-1 linux-4.9 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- ELSA-2020-5437 Important: kernel security and bug fix update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Dec 16, 2020
- ELSA-2020-5715 Important: Unbreakable Enterprise kernel security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Jun 9, 2020
References
- https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.3.10
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=55667441c84fa5e0911a0aac44fb059c15ba6da2
- https://security.netapp.com/advisory/ntap-20200204-0002/
- [debian-lts-announce] 20200302 [SECURITY] [DLA 2114-1] linux-4.9 security update mailing-list
- https://www.computer.org/csdl/proceedings-article/sp/2020/349700b594/1j2LgrHDR2o