CVE-2021-22555
Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE
- High 8.3
- Exploited: added to CISA KEV 6 Oct 2025
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
Key facts
- Published
- 7 Jul 2021
- Last changed
- 30 Dec 2025
- Assigned by
- KEV added
- 6 Oct 2025
- KEV fix due
- 27 Oct 2025
- EPSS
- 78.684% likely to be exploited in the next 30 days, higher than 99.595% of CVEs (scores for 15 Nov 2026)
- SSVC (CISA)
- Exploitation: active; Automatable: no; Technical impact: total
Severity scores
Each score is shown as its source gave it. They are not averaged or merged.
- 8.3CVSS 3.1, Highfrom the CNA (Google)
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
What 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 KEV required action
Historical context and remediation
This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.
No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.
Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.
Affected products
| Vendor | Product | Versions |
|---|---|---|
| n/a | Linux Kernel |
|
Timeline
- 7 Jul 2021 Published
- 6 Oct 2025 Added to the CISA KEV catalogue