CVE-2021-3444: Linux kernel bpf verifier incorrect mod32 truncation
Noroxi assessment
Priority: Monitor (action score 31/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.61% (FIRST EPSS).
- 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.
- Fixed version: linux (Debian:12) 5.10.19-1; linux-4.19 (Debian:9) 4.19.208-1~deb9u1; kernel-default (SUSE:Linux Enterprise High Availability Extension 12 SP5) 4.12.14-122.71.1.
Low priority for now. Upgrade to linux (Debian:12) 5.10.19-1; linux-4.19 (Debian:9) 4.19.208-1~deb9u1; kernel-default (SUSE:Linux Enterprise High Availability Extension 12 SP5) 4.12.14-122.71.1 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
The bpf verifier in the Linux kernel did not properly handle mod32 destination register truncation when the source register was known to be 0. A local attacker with the ability to load bpf programs could use this gain out-of-bounds reads in kernel memory leading to information disclosure (kernel memory), and possibly out-of-bounds writes that could potentially lead to code execution. This issue was addressed in the upstream kernel in commit 9b00f1b78809 ("bpf: Fix truncation handling for mod32 dst reg wrt zero") and in Linux stable kernels 5.11.2, 5.10.19, and 5.4.101.
- Published
- Mar 23, 2021
- Updated
- Jun 17, 2026
- EPSS
- 0.6% · 49th percentile
- CWE
- CWE-681
Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 31 / 40 · 7.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.6%
CNA vs NVD score
- NVD
- 7.8
- CNA · canonical
- 7.8
- agree
CVSS:3.1/AV:L/AC:H/PR:L/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.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
| canonical | ubuntu linux | cpe:2.3:o:canonical:ubuntu_linux |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- canonical ubuntu linux14.04
- canonical ubuntu linux16.04
- canonical ubuntu linux18.04
- canonical ubuntu linux20.04
- debian debian linux9.0
- linux linux kernel5.11 and later · before 5.11.2
- linux linux kernel5.5.0 and later · before 5.10.19
- linux linux kernelbefore 5.4.101
Versions reported by the vendor
Affected version ranges reported by the assigning authority (canonical). Independent of NVD's CPE analysis and usually ahead of it.
Linux kernel
- trunk and later · before 5.12-rc1affected
- 5.11 and later · before 5.11.2affected
- 5.10 and later · before 5.10.19affected
- 5.4 and later · before 5.4.101affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | linux | before 5.10.19-1 | 5.10.19-1 |
| Debian:9 | linux-4.19 | before 4.19.208-1~deb9u1 | 4.19.208-1~deb9u1 |
| SUSE:Linux Enterprise High Availability Extension 12 SP5 | kernel-default | before 4.12.14-122.71.1 | 4.12.14-122.71.1 |
| SUSE:Linux Enterprise Live Patching 12 SP4 | kgraft-patch-SLE12-SP4_Update_13 | before 11-2.2 | 11-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP4 | kgraft-patch-SLE12-SP4_Update_14 | before 9-2.2 | 9-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP4 | kgraft-patch-SLE12-SP4_Update_15 | before 9-2.2 | 9-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP4 | kgraft-patch-SLE12-SP4_Update_16 | before 8-2.2 | 8-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP4 | kgraft-patch-SLE12-SP4_Update_17 | before 5-2.2 | 5-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP4 | kgraft-patch-SLE12-SP4_Update_18 | before 4-2.2 | 4-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP4 | kgraft-patch-SLE12-SP4_Update_19 | before 3-2.2 | 3-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_10 | before 9-2.2 | 9-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_11 | before 7-2.2 | 7-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_12 | before 7-2.2 | 7-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_13 | before 5-2.2 | 5-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_14 | before 5-2.2 | 5-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_15 | before 4-2.2 | 4-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_16 | before 3-2.2 | 3-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_17 | before 2-2.2 | 2-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_18 | before 1-8.5.1 | 1-8.5.1 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_4 | before 12-2.2 | 12-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_5 | before 11-2.2 | 11-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_6 | before 11-2.2 | 11-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_7 | before 11-2.2 | 11-2.2 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_8 | before 11-2.2 | 11-2.2 |
+37
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV90Now
- 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-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV85Now
Published before and after this one in the same product
- ← EarlierCVE-2021-28972Mar 22, 2021 · In drivers/pci/hotplug/rpadlpar_sysfs.c in the Linux kernel through 5.11.8, the RPA PCI Hotplug driver has a user-tolerable buffer overflow 26Monitor
- ← EarlierCVE-2021-20219Mar 23, 2021 · A denial of service vulnerability was found in n_tty_receive_char_special in drivers/tty/n_tty.c of the Linux kernel.22Monitor
- Later →CVE-2020-35508Mar 26, 2021 · A flaw possibility of race condition and incorrect initialization of the process id was found in the Linux kernel child/parent process ident18Monitor
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 |
|---|---|---|
| debian:linux | 5.10.19-1 · Debian:12 | Package registry (OSV) |
| debian:linux-4.19 | 4.19.208-1~deb9u1 · Debian:9 | Package registry (OSV) |
| suse:kernel-livepatch-SLE15_Update_18 | 9-2.2 · SUSE:Linux Enterprise Live Patching 15 | Package registry (OSV) |
| suse:kernel-livepatch-SLE15_Update_19 | 9-2.2 · SUSE:Linux Enterprise Live Patching 15 | Package registry (OSV) |
| suse:kernel-livepatch-SLE15_Update_20 | 8-2.2 · SUSE:Linux Enterprise Live Patching 15 | Package registry (OSV) |
| suse:kernel-livepatch-SLE15_Update_21 | 6-2.2 · SUSE:Linux Enterprise Live Patching 15 | Package registry (OSV) |
| suse:kernel-livepatch-SLE15_Update_22 | 4-2.2 · SUSE:Linux Enterprise Live Patching 15 | Package registry (OSV) |
| suse:kgraft-patch-SLE12-SP4_Update_13 | 11-2.2 · SUSE:Linux Enterprise Live Patching 12 SP4 | Package registry (OSV) |
| suse:kgraft-patch-SLE12-SP4_Update_14 | 9-2.2 · SUSE:Linux Enterprise Live Patching 12 SP4 | Package registry (OSV) |
| suse:kgraft-patch-SLE12-SP4_Update_15 | 9-2.2 · SUSE:Linux Enterprise Live Patching 12 SP4 | Package registry (OSV) |
| suse:kgraft-patch-SLE12-SP4_Update_16 | 8-2.2 · SUSE:Linux Enterprise Live Patching 12 SP4 | Package registry (OSV) |
| suse:kgraft-patch-SLE12-SP4_Update_17 | 5-2.2 · SUSE:Linux Enterprise Live Patching 12 SP4 | Package registry (OSV) |
| suse:kgraft-patch-SLE12-SP4_Update_18 | 4-2.2 · SUSE:Linux Enterprise Live Patching 12 SP4 | Package registry (OSV) |
| suse:kgraft-patch-SLE12-SP4_Update_19 | 3-2.2 · SUSE:Linux Enterprise Live Patching 12 SP4 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
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.
No dated events beyond publication.
No history yet (it accumulates with the daily EPSS job).
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.
- De4dCr0w360 Alpha Lab
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-681 · Incorrect Conversion between Numeric TypesCVSS 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.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (6 more)Show less
- packetstormsecurity.com/files/164950/Kernel-Live-Patch-Security-Notice-LSN-0082-1.html
- www.openwall.com/lists/oss-security/2021/03/23/2
- git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9b00f1b78809
- lists.debian.org/debian-lts-announce/2021/10/msg00010.html
- security.netapp.com/advisory/ntap-20210416-0006/
- www.openwall.com/lists/oss-security/2021/03/23/2
Vendor advisories and official records. Exploit/PoC links are deliberately left out.