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Vulnerability record · CVE-2021-33909 · published 20 July 2021

CVE-2021-33909: Linux kernel integer overflow vulnerability

Linux · Linux Kernel

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.

7.8 CVSS 3.1 High EPSS 9.7% · top 4.6% CWE-190 · Integer overflowCWE-787 · Out-of-bounds write
7.8CVSS 3.1 base score, v2 7.2
9.7%EPSS exploitation probability, 30 days
NoNot in CISA KEV
7Affected product versions listed by NVD
40References, 4 tagged exploit
17 Jun 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

7 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.html ExploitThird Party AdvisoryVDB Entry
http://packetstormsecurity.com/files/163671/Kernel-Live-Patch-Security-Notice-LSN-0079-1.html Third Party AdvisoryVDB Entry
http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html Third Party AdvisoryVDB Entry
http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html Third Party AdvisoryVDB Entry
http://www.openwall.com/lists/oss-security/2021/07/22/7 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/08/25/10 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/09/17/2 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/09/17/4 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/09/21/1 Mailing ListThird Party Advisory
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.13.4 Mailing ListPatchVendor Advisory
https://github.com/torvalds/linux/commit/8cae8cd89f05f6de223d63e6d15e31c8ba9cf53b PatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/07/msg00014.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/07/msg00015.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/07/msg00016.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Z4UHHIGISO3FVRF4CQNJS4I
https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2022-0015 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210819-0004/ Third Party Advisory
https://www.debian.org/security/2021/dsa-4941 Third Party Advisory
https://www.openwall.com/lists/oss-security/2021/07/20/1 ExploitMailing ListThird Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html PatchThird Party Advisory
http://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.html ExploitThird Party AdvisoryVDB Entry
http://packetstormsecurity.com/files/163671/Kernel-Live-Patch-Security-Notice-LSN-0079-1.html Third Party AdvisoryVDB Entry
http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html Third Party AdvisoryVDB Entry
http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html Third Party AdvisoryVDB Entry
http://www.openwall.com/lists/oss-security/2021/07/22/7 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/08/25/10 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/09/17/2 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/09/17/4 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/09/21/1 Mailing ListThird Party Advisory
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.13.4 Mailing ListPatchVendor Advisory
https://github.com/torvalds/linux/commit/8cae8cd89f05f6de223d63e6d15e31c8ba9cf53b PatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/07/msg00014.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/07/msg00015.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/07/msg00016.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Z4UHHIGISO3FVRF4CQNJS4I
https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2022-0015 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210819-0004/ Third Party Advisory
https://www.debian.org/security/2021/dsa-4941 Third Party Advisory
https://www.openwall.com/lists/oss-security/2021/07/20/1 ExploitMailing ListThird Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-33909), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.