Description
A flaw possibility of race condition and incorrect initialization of the process id was found in the Linux kernel child/parent process identification handling while filtering signal handlers. A local attacker is able to abuse this flaw to bypass checks to send any signal to a privileged process.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| — | kernel | kernel 5.12 | — |
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 | 5.9.9-1 | — |
| Debian 13 | linux | 5.9.9-1 | — |
| Debian 12 | linux | 5.9.9-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 24.04 LTS | linux-raspi-realtime | No fix yet | — |
| Ubuntu 22.04 LTS | linux-realtime +1 | No fix yet | — |
| Ubuntu 20.04 LTS | linux | 5.4.0-59.65 | — |
| Ubuntu 20.04 LTS | linux-aws | 5.4.0-1034.35 | — |
| Ubuntu 20.04 LTS | linux-azure | 5.4.0-1035.36 | — |
| Ubuntu 20.04 LTS | linux-gcp | 5.4.0-1033.35 | — |
| Ubuntu 20.04 LTS | linux-hwe-5.8 | 5.8.0-44.50~20.04.1 | USN-4751-1 |
| Ubuntu 20.04 LTS | linux-kvm | 5.4.0-1031.32 | — |
| Ubuntu 20.04 LTS | linux-oem-5.6 | 5.6.0-1048.52 | USN-4752-1 |
| Ubuntu 20.04 LTS | linux-oracle | 5.4.0-1034.36 | — |
| Ubuntu 20.04 LTS | linux-raspi | 5.4.0-1026.29 | — |
| Ubuntu 20.04 LTS | linux-riscv +1 | No fix yet | — |
| Ubuntu 20.04 LTS | linux-riscv-5.8 | 5.8.0-17.19~20.04.1 | — |
| Ubuntu 18.04 LTS | linux | 4.15.0-129.132 | — |
| Ubuntu 18.04 LTS | linux-aws | 4.15.0-1091.96 | — |
| Ubuntu 18.04 LTS | linux-aws-5.4 | 5.4.0-1034.35~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-azure-4.15 | 4.15.0-1103.114 | — |
| Ubuntu 18.04 LTS | linux-azure-5.4 | 5.4.0-1035.36~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-dell300x | 4.15.0-1010.14 | — |
| Ubuntu 18.04 LTS | linux-gcp +12 | No fix yet | — |
| Ubuntu 18.04 LTS | linux-gcp-4.15 | 4.15.0-1091.104 | — |
| Ubuntu 18.04 LTS | linux-gcp-5.4 +1 | 5.4.0-1033.35~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-gkeop-5.4 | 5.4.0-1008.9~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-hwe-5.4 | 5.4.0-59.65~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-kvm | 4.15.0-1082.84 | — |
| Ubuntu 18.04 LTS | linux-oracle | 4.15.0-1062.68 | — |
| Ubuntu 18.04 LTS | linux-oracle-5.4 | 5.4.0-1034.36~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-raspi-5.4 | 5.4.0-1026.29~18.04.1 | — |
| Ubuntu 18.04 LTS | linux-raspi2 +1 | 4.15.0-1077.82 | — |
| Ubuntu 18.04 LTS | linux-snapdragon | 4.15.0-1094.103 | — |
| Ubuntu 16.04 LTS | linux | 4.4.0-198.230 | — |
| Ubuntu 16.04 LTS | linux-aws | 4.4.0-1119.133 | — |
| Ubuntu 16.04 LTS | linux-aws-hwe | 4.15.0-1091.96~16.04.1 | — |
| Ubuntu 16.04 LTS | linux-azure | 4.15.0-1103.114~16.04.1 | — |
| Ubuntu 16.04 LTS | linux-gcp | 4.15.0-1091.104~16.04.1 | — |
| Ubuntu 16.04 LTS | linux-hwe | 4.15.0-129.132~16.04.1 | — |
| Ubuntu 16.04 LTS | linux-hwe-edge | No fix yet | — |
| Ubuntu 16.04 LTS | linux-kvm | 4.4.0-1085.94 | — |
| Ubuntu 16.04 LTS | linux-oracle | 4.15.0-1062.68~16.04.1 | — |
| Ubuntu 16.04 LTS | linux-raspi2 | 4.4.0-1143.153 | — |
| Ubuntu 16.04 LTS | linux-snapdragon | 4.4.0-1147.157 | — |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro FIPS 20.04 LTS | linux-aws-fips +2 | No fix yet | — |
| Ubuntu Pro FIPS 18.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS 16.04 LTS | linux-fips | No fix yet | — |
| Ubuntu Pro FIPS-updates 20.04 LTS | linux-aws-fips | 5.4.0-1069.73+fips2 | — |
| Ubuntu Pro FIPS-updates 20.04 LTS | linux-azure-fips | 5.4.0-1073.76+fips1 | — |
| Ubuntu Pro FIPS-updates 20.04 LTS | linux-gcp-fips | 5.4.0-1067.71~20.04.1 | — |
| Ubuntu Pro FIPS-updates 18.04 LTS | linux-aws-fips | 4.15.0-2034.35 | — |
| Ubuntu Pro FIPS-updates 18.04 LTS | linux-azure-fips | 4.15.0-2016.18 | — |
| Ubuntu Pro FIPS-updates 18.04 LTS | linux-fips | 4.15.0-1049.56 | — |
| Ubuntu Pro FIPS-updates 16.04 LTS | linux-fips | 4.4.0-1052.58 | — |
| Ubuntu Pro 14.04 LTS | linux | No fix yet | — |
| Ubuntu Pro 14.04 LTS | linux-aws | 4.4.0-1083.87 | — |
| Ubuntu Pro 14.04 LTS | linux-azure | 4.15.0-1103.114~14.04.1 | — |
| Ubuntu Pro 14.04 LTS | linux-lts-xenial | 4.4.0-198.230~14.04.1 | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | kernel-rt +12 | 4.18.0-305.rt7.72.el8 | RHSA-2021:1739 |
| RHEL 8 | perf +26 | 4.18.0-305.el8 | RHSA-2021:1578 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.2 EUS | kernel-rt +12 | 4.18.0-193.60.2.rt13.112.el8_2 | RHSA-2021:2719 |
| RHEL 8.2 EUS | perf +26 | 4.18.0-193.60.2.el8_2 | RHSA-2021:2718 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | kernel-tools-libs-devel | 4.18.0-305.el8 | ALSA-2021:1578 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 2 (CBL-Mariner) | kernel | 5.10.78.1-1 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | perf +19 | 4.18.0-305.el8 | ELSA-2021-1578 |
| Oracle Linux 7 | kernel-uek +5 | 4.1.12-124.50.2.el7uek | ELSA-2021-9215 |
Advisories 9
- ALSA-2021:1578 Important: kernel security, bug fix, and enhancement update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2021:2718 Red Hat Security Advisory: kernel security and bug fix update Red Hat Security Advisories (RHSA) · Aug 14, 2026
- RHSA-2021:2719 Red Hat Security Advisory: kernel-rt security and bug fix update Red Hat Security Advisories (RHSA) · Aug 14, 2026
- RHSA-2021:1739 Red Hat Security Advisory: kernel-rt security and bug fix update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:1578 Red Hat Security Advisory: kernel security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- USN-4752-1 linux-oem-5.6 vulnerabilities Ubuntu Security Notices (USN) · Jun 3, 2026
- USN-4751-1 linux, linux-aws, linux-azure, linux-gcp, linux-hwe-5.8, linux-kvm, linux-oracle, linux-raspi vulnerabilities Ubuntu Security Notices (USN) · Jun 3, 2026
- ELSA-2021-1578 Important: kernel security, bug fix, and enhancement update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · May 25, 2021
- ELSA-2021-9215 Important: Unbreakable Enterprise kernel security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · May 6, 2021