Raw vector
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2021-22555 is a high-severity Out-of-bounds Write (CWE-787) vulnerability in Linux Linux Kernel. Its CVSS base score is 8.3 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Security Account Manager (T1003.002); ranked in the top 0.4% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
A heap out-of-bounds write vulnerability was discovered in the Linux kernel's net/netfilter/x_tables.c file, affecting versions since v2.6.19-rc1. The flaw, assigned CVE-2021-22555 and CWE-787, resides in the netfilter subsystem and can result in heap memory corruption.
An attacker with access to a user namespace can exploit the issue to escalate privileges or trigger a denial of service. The vulnerability carries a CVSS 3.1 score of 8.3, reflecting an adjacent-network attack vector with high complexity but no required privileges or user interaction, and potential impact across confidentiality, integrity, and availability in certain configurations.
Public references include multiple kernel live-patch notices (LSN-0080-1, LSN-0081-1, LSN-0083-1) that address the flaw, along with proof-of-concept code demonstrating privilege-escalation and heap-out-of-bounds write exploitation.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-9696
Vulnerability Data
A heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c. This allows an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space
- CWE(s)
- KEV Date Added
- 06 October 2025
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Out-of-bounds writes that corrupt control flow or inject shellcode are rendered non-executable by the same memory protections.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Vulnerability scanning and recording can discover out-of-bounds write flaws so they can be remediated.
Patching or replacing vulnerable software directly eliminates known instances of this coding weakness.
Secure-development practices (static analysis, bounds checking, code review) are the primary means of preventing out-of-bounds writes.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.