CVE-2021-22555
Linux Kernel: Heap Out-of-Bounds Write
As of , CVE-2021-22555 in Linux Kernel is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch this week.
- Exploited
- Yes: CISA listed it on 6 October 2025
- US federal deadline
- 27 October 202521 days after CISA listed it. US federal civilian agencies must fix it by then.
- Used in ransomware campaigns
- Not known to CISA
- EPSS score
- 0.79Higher than 99% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
- Public exploit
- 1 Metasploit module and 1 Exploit-DB entry (1 verified)
- Fix
- Vendor advice: git.kernel.org, github.com and security.netapp.comLinks below, from CISA's entry.
What CISA says to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA's required action
What the flaw is
Linux Kernel contains a heap out-of-bounds write vulnerability that could allow an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space.
CISA's description
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
The CVE record's description, from Google
- CVE published
- 7 July 2021
- Assigned by
- CVSS
- 8.3 High (CVSS 3.1, from the CNA)
- CWE-787
- Out-of-bounds Write
- CISA SSVC, exploitation
- active
- CISA SSVC, automatable
- no
- CISA SSVC, technical impact
- total
Timeline
- The CVE record was published.
- Exploit-DB published an exploit (EDB-ID 50135).
- CISA added it to its list of exploited vulnerabilities.
- The US federal deadline to fix it.
Public exploits
Facts from Metasploit's module list and Exploit-DB's index; we never copy exploit code.
- Metasploit: Netfilter x_tables Heap OOB Write Privilege Escalationexploit module, rank great
- Exploit-DB: Linux Kernel 2.6.19 < 5.9 - 'Netfilter Local Privilege EscalationEDB-ID 50135, verified by Exploit-DB, 15 July 2021
Kernel: other exploited entries
| Vulnerability | Product | Our group | Listed | Deadline | EPSS |
|---|---|---|---|---|---|
| CVE-2025-39682Improper Check for Unusual or Exceptional Conditions | Linux Kernel | Patch nowForensic triage required by CISA | 0.03 | ||
| CVE-2025-39964Race Condition | Linux Kernel | Patch nowForensic triage required by CISA | 0.01 | ||
| CVE-2026-53266Out-of-Bounds Write | Linux Kernel | Patch nowForensic triage required by CISA | 0.01 | ||
| CVE-2026-53362Unspecified | Linux Kernel | Patch nowForensic triage required by CISA | 0.01 | ||
| CVE-2013-6282Improper Input Validation | Linux Kernel | Patch this weekMetasploit module; verified Exploit-DB entry | 0.40 | ||
| CVE-2019-13272Improper Privilege Management | Linux Kernel | Patch this weekMetasploit module; EPSS 0.52; verified Exploit-DB entry | 0.52 | ||
| CVE-2010-3904Improper Input Validation | Linux Kernel | Patch this weekMetasploit module; verified Exploit-DB entry | 0.16 | ||
| CVE-2022-0847Privilege Escalation | Linux Kernel | Patch this weekMetasploit module; EPSS 0.93 | 0.93 | ||
| CVE-2021-3493Privilege Escalation | Linux Kernel | Patch this weekMetasploit module | 0.49 | ||
| CVE-2014-3153Privilege Escalation | Linux Kernel | Patch this weekMetasploit module | 0.37 |
Read further
- CVE recordcve.org
- NVD entrynvd.nist.gov
- CISA's catalogcisa.gov
- EPSS for this CVEapi.first.org