HIGH
CVE-2021-33909
CWE-190Published: July 20, 2021· Updated: Jun 17, 2026
7.8
CVSS v3.1
Official 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.
Technical Analysis
CVE-2021-33909 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 7.8.
CVSS v3.1 Vector Breakdown
Exploitability
Attack VectorLocal
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Affected Vendors & Products
Exploit & PoC Resources
NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.
Official Patches & Advisories
ADVISORYhttp://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.html
ADVISORYhttp://packetstormsecurity.com/files/163671/Kernel-Live-Patch-Security-Notice-LSN-0079-1.html
ADVISORYhttp://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html
ADVISORYhttp://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html
ADVISORYhttp://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.html
ADVISORYhttp://packetstormsecurity.com/files/163671/Kernel-Live-Patch-Security-Notice-LSN-0079-1.html
ADVISORYhttp://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html
All References (40)
→
http://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.htmlExploit · Third Party Advisory · VDB Entry
→
http://packetstormsecurity.com/files/163671/Kernel-Live-Patch-Security-Notice-LSN-0079-1.htmlThird Party Advisory · VDB Entry
→
http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.htmlThird Party Advisory · VDB Entry
→
http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.htmlThird Party Advisory · VDB Entry
→
http://www.openwall.com/lists/oss-security/2021/07/22/7Mailing List · Third Party Advisory
→
http://www.openwall.com/lists/oss-security/2021/08/25/10Mailing List · Third Party Advisory
→
http://www.openwall.com/lists/oss-security/2021/09/17/2Mailing List · Third Party Advisory
→
http://www.openwall.com/lists/oss-security/2021/09/17/4Mailing List · Third Party Advisory
→
http://www.openwall.com/lists/oss-security/2021/09/21/1Mailing List · Third Party Advisory
→
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.13.4Mailing List · Patch · Vendor Advisory
→
https://github.com/torvalds/linux/commit/8cae8cd89f05f6de223d63e6d15e31c8ba9cf53bPatch · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2021/07/msg00014.htmlMailing List · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2021/07/msg00015.htmlMailing List · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2021/07/msg00016.htmlMailing List · Third Party Advisory
Quick Facts
CVE IDCVE-2021-33909
CVSS Score7.8 / 10
SeverityHIGH
WeaknessCWE-190
CISA KEVNo
Affected6 vendor(s)
PublishedJul 20, 2021
Related CVEs (CWE-190)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-33909 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.