CVE-2021-33909: Debian Linux

High severity, CVSS 7.8. EPSS: 9.7% chance of exploitation in the next 30 days.

fs/seq_file.c in the Linux kernel 3.16 through 5.13.x before 5.13.4 does not properly restrict seq buffer allocations, leading to an integer overflow, an Out-of-bounds Write, and escalation to root by an unprivileged user, aka CID-8cae8cd89f05.

Affected products

• Debian Debian Linux: version 9.0 only; version 10.0 only
• Fedoraproject Fedora: version 34 only
• Linux Linux Kernel: from 3.12.43, before 3.13 (fixed in 3.13); from 3.16, before 4.4.276 (fixed in 4.4.276); from 4.5, before 4.9.276 (fixed in 4.9.276); from 4.10, before 4.14.240 (fixed in 4.14.240); from 4.15, before 4.19.198 (fixed in 4.19.198); from 4.20, before 5.4.134 (fixed in 5.4.134); …
• Netapp Hci Management Node: affected versions not specified
• Netapp Solidfire: affected versions not specified
• Oracle Communications Session Border Controller: version 8.2 only; version 8.3 only; version 8.4 only; version 9.0 only
• SonicWall SMA1000 Firmware: up to and including 12.4.2-02044

Published 2021-07-20. Last modified 2026-06-17.