Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE
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
- BDU:2021-04260
- ALSA-2021:3057
- openSUSE-SU-2021:1076-1
- openSUSE-SU-2021:2409-1
- openSUSE-SU-2021:2415-1
- openSUSE-SU-2021:2427-1
- RHSA-2021:3044
- RHSA-2021:3057
- RHSA-2021:3088
- RHSA-2021:3173
- RHSA-2021:3181
- RHSA-2021:3235
- RHSA-2021:3321
- RHSA-2021:3327
- RHSA-2021:3328
- RHSA-2021:3363
- RHSA-2021:3375
- RHSA-2021:3380
- RHSA-2021:3381
- RHSA-2021:3399
- Published
- Jul 7, 2021
- Updated
- Jun 16, 2026
- EPSS
- 78.7% · 100th percentile
- CWE
- CWE-787
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Report tools
Action score
85
Now
Patch today or shut off access.
- CVSS
- 31 / 40 · 7.8 / 10
- CISA KEV
- 30 / 30 · Listed
- EPSS
- 24 / 30 · 78.7%
CISA SSVC decision
- Exploitation
- active
- Automatable
- no
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 7.8
- CNA · Google
- 8.3
- 0.5 point gap
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Actively exploited in the wild
CISA added this to its Known Exploited Vulnerabilities catalog on Oct 6, 2025. That signals real attacks, not theory.
Remediation deadline for government agencies: Oct 27, 2025.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
| netapp | c400 firmware | cpe:2.3:o:netapp:c400_firmware |
| netapp | c400 | cpe:2.3:h:netapp:c400 |
| netapp | c250 firmware | cpe:2.3:o:netapp:c250_firmware |
| netapp | c250 | cpe:2.3:h:netapp:c250 |
| netapp | h410c firmware | cpe:2.3:o:netapp:h410c_firmware |
| netapp | h410c | cpe:2.3:h:netapp:h410c |
| netapp | h300s firmware | cpe:2.3:o:netapp:h300s_firmware |
| netapp | h300s | cpe:2.3:h:netapp:h300s |
| netapp | h500s firmware | cpe:2.3:o:netapp:h500s_firmware |
| netapp | h500s | cpe:2.3:h:netapp:h500s |
| netapp | h700s firmware | cpe:2.3:o:netapp:h700s_firmware |
and 24 more
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- brocade fabric operating systemall versions
- linux linux kernel4.20 and later · before 5.4.113
- linux linux kernel4.5 and later · before 4.9.267
- linux linux kernel4.10 and later · before 4.14.231
- linux linux kernel4.15 and later · before 4.19.188
- linux linux kernel5.5 and later · before 5.10.31
- linux linux kernel5.11 and later · before 5.12
- linux linux kernel2.6.19 and later · before 4.4.267
- netapp aff 500f firmwareall versions
- netapp aff a250 firmwareall versions
- netapp aff a400 firmwareall versions
- netapp c250 firmwareall versions
- netapp c400 firmwareall versions
- netapp cloud backupall versions
- netapp fas 8300 firmwareall versions
- netapp fas 8700 firmwareall versions
- netapp h300s firmwareall versions
- netapp h410c firmwareall versions
- netapp h410s firmwareall versions
- netapp h500s firmwareall versions
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Google). Independent of NVD's CPE analysis and usually ahead of it.
n/a Linux Kernel
- 2.6.19-rc1 and later · before unspecifiedaffected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:8 | kernel-tools-libs-devel | before 4.18.0-305.12.1.el8_4 | 4.18.0-305.12.1.el8_4 |
| Debian:12 | linux | before 5.10.38-1 | 5.10.38-1 |
| openSUSE:Leap 15.2 | kernel-debug | before 5.3.18-lp152.84.1 | 5.3.18-lp152.84.1 |
| openSUSE:Leap 15.2 | kernel-default | before 5.3.18-lp152.84.1 | 5.3.18-lp152.84.1 |
| openSUSE:Leap 15.2 | kernel-default-base | before 5.3.18-lp152.84.1.lp152.8.38.1 | 5.3.18-lp152.84.1.lp152.8.38.1 |
| openSUSE:Leap 15.2 | kernel-docs | before 5.3.18-lp152.84.1 | 5.3.18-lp152.84.1 |
| openSUSE:Leap 15.2 | kernel-kvmsmall | before 5.3.18-lp152.84.1 | 5.3.18-lp152.84.1 |
| openSUSE:Leap 15.2 | kernel-obs-build | before 5.3.18-lp152.84.1 | 5.3.18-lp152.84.1 |
| openSUSE:Leap 15.2 | kernel-obs-qa | before 5.3.18-lp152.84.1 | 5.3.18-lp152.84.1 |
| openSUSE:Leap 15.2 | kernel-preempt | before 5.3.18-lp152.84.1 | 5.3.18-lp152.84.1 |
| openSUSE:Leap 15.2 | kernel-source | before 5.3.18-lp152.84.1 | 5.3.18-lp152.84.1 |
| openSUSE:Leap 15.2 | kernel-syms | before 5.3.18-lp152.84.1 | 5.3.18-lp152.84.1 |
| openSUSE:Leap 15.3 | kernel-64kb | before 5.3.18-59.16.1 | 5.3.18-59.16.1 |
| openSUSE:Leap 15.3 | kernel-azure | before 5.3.18-38.14.1 | 5.3.18-38.14.1 |
| openSUSE:Leap 15.3 | kernel-debug | before 5.3.18-59.16.1 | 5.3.18-59.16.1 |
| openSUSE:Leap 15.3 | kernel-debug | before 4.12.14-197.99.1 | 4.12.14-197.99.1 |
| openSUSE:Leap 15.3 | kernel-default | before 5.3.18-59.16.1 | 5.3.18-59.16.1 |
| openSUSE:Leap 15.3 | kernel-default | before 4.12.14-197.99.1 | 4.12.14-197.99.1 |
| openSUSE:Leap 15.3 | kernel-default-base | before 5.3.18-59.16.1.18.8.1 | 5.3.18-59.16.1.18.8.1 |
| openSUSE:Leap 15.3 | kernel-docs | before 5.3.18-59.16.1 | 5.3.18-59.16.1 |
| openSUSE:Leap 15.3 | kernel-kvmsmall | before 4.12.14-197.99.1 | 4.12.14-197.99.1 |
| openSUSE:Leap 15.3 | kernel-kvmsmall | before 5.3.18-59.16.1 | 5.3.18-59.16.1 |
| openSUSE:Leap 15.3 | kernel-obs-build | before 5.3.18-59.16.1 | 5.3.18-59.16.1 |
| openSUSE:Leap 15.3 | kernel-obs-qa | before 5.3.18-59.16.1 | 5.3.18-59.16.1 |
+96
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV89Now
- CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV83Now
- CVE-2019-13272In the Linux kernel before 5.1.17, ptrace_link in kernel/ptrace.c mishandles the recording of the credentials of a process that wants to creKEV77This week
- CVE-2013-6282The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the v6k and v7 ARM platforms do not validate certain addKEV77This week
- CVE-2013-2094The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9 uses an incorrect integer data type, which allows loKEV77This week
- CVE-2014-3153The futex_requeue function in kernel/futex.c in the Linux kernel through 3.14.5 does not ensure that calls have two different futex addresseKEV72This week
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| almalinux:kernel-tools-libs-devel | 4.18.0-305.12.1.el8_4 · AlmaLinux:8 | Package registry (OSV) |
| debian:linux | 5.10.38-1 · Debian:12 | Package registry (OSV) |
| opensuse:kernel-azure | 5.3.18-38.14.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-debug | 5.3.18-lp152.84.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:kernel-default | 5.3.18-lp152.84.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:kernel-default-base | 5.3.18-lp152.84.1.lp152.8.38.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:kernel-docs | 5.3.18-lp152.84.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:kernel-kvmsmall | 5.3.18-lp152.84.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:kernel-obs-build | 5.3.18-lp152.84.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:kernel-obs-qa | 5.3.18-lp152.84.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:kernel-preempt | 5.3.18-lp152.84.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:kernel-source | 5.3.18-lp152.84.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:kernel-source-azure | 5.3.18-38.14.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-syms | 5.3.18-lp152.84.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305 | 0:1-4.el8 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305_10_2 | 0:1-1.el8_4 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305_10_2-debuginfo | 0:1-1.el8_4 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305_10_2-debugsource | 0:1-1.el8_4 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305_3_1 | 0:1-3.el8_4 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305_3_1-debuginfo | 0:1-3.el8_4 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305_3_1-debugsource | 0:1-3.el8_4 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305_7_1 | 0:1-2.el8_4 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305_7_1-debuginfo | 0:1-2.el8_4 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305_7_1-debugsource | 0:1-2.el8_4 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305-debuginfo | 0:1-4.el8 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:kpatch-patch-4_18_0-305-debugsource | 0:1-4.el8 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| rocky linux:kernel | 0:4.18.0-305.12.1.el8_4 · Rocky Linux:8 | Package registry (OSV) |
| rocky linux:kernel-rt | 0:4.18.0-305.12.1.rt7.84.el8_4 · Rocky Linux:8 | Package registry (OSV) |
| suse:kernel-64kb | 5.3.18-59.16.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP3 | Package registry (OSV) |
| suse:kernel-azure | 4.12.14-16.65.1 · SUSE:Linux Enterprise Server 12 SP5 | Package registry (OSV) |
+10
Exploit status
Weaponized
A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.
Evidence
- Metasploit module ×1
- Exploit-DB entry ×1
- Proof-of-concept repository on GitHub ×13
Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.
| Source | Kind | Date |
|---|---|---|
| Exploit-DB entry | local | 2021-07-15 |
| Metasploit module | exploit/linux/local/netfilter_xtables_heap_oob_write_priv_escNetfilter x_tables Heap OOB Write Privilege Escalationexploit | 2021-07-07 |
| Proof-of-concept repository on GitHub | stars:1 | 2021-07-15 |
| Proof-of-concept repository on GitHub | stars:14 | 2021-07-16 |
| Proof-of-concept repository on GitHub | stars:4 | 2021-07-16 |
| Proof-of-concept repository on GitHub | stars:1 | 2021-10-01 |
| Proof-of-concept repository on GitHub | stars:40 | 2022-04-05 |
| Proof-of-concept repository on GitHub | stars:1 | 2023-05-10 |
| Proof-of-concept repository on GitHub | stars:3 | 2023-08-05 |
| Proof-of-concept repository on GitHub | stars:0 | 2023-08-20 |
| Proof-of-concept repository on GitHub | stars:0 | 2024-02-05 |
| Proof-of-concept repository on GitHub | stars:0 | 2024-02-27 |
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- Metasploitsame day
- Published
- First PoC+8 d
- CISA KEV+1552 d
- TodaySep 30, 2026+1912 d
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- A low-privileged account is enough.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-787 · Out-of-bounds WriteCVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.html
- git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21
- git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d
- security.netapp.com/advisory/ntap-20210805-0010/
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22555
Vendor advisories and official records. Exploit/PoC links are deliberately left out.