Linux kernel bpf verifier incorrect mod32 truncation
Priority LOW 35CWE-681Published · Updated
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- High
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 2 fixed, 1 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.
Summary
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.
Why it matters now
EPSS 0.0061 49th percentileScored 2026-11-07
Fix Partial kernel (Linux): 5.12-rc1, 5.11.2, 5.10.19 +1Red Hat: 1 advisoryRed Hat: 2 fixed, 1 without a fix
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | kernel | trunk to before 5.12-rc1; 5.11 to before 5.11.2; 5.10 to before 5.10.19; 5.4 to before 5.4.101 | 5.12-rc1, 5.11.2, 5.10.19, 5.4.101 | Patch available | CNA |
- kernel VendorLinux Affected trunk to before 5.12-rc1; 5.11 to before 5.11.2; 5.10 to before 5.10.19; 5.4 to before 5.4.101 Fixed in 5.12-rc1, 5.11.2, 5.10.19, 5.4.101 Patch available CNA
CPE configurations NVD · 6
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | before 5.4.101; 5.5.0 to before 5.10.19; 5.11 to before 5.11.2 | Vulnerable | Linux |
| cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* | 9.0 | Vulnerable | Debian |
| cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:esm:*:*:* | 14.04 | Vulnerable | Canonical |
| cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:* | 16.04 | Vulnerable | Canonical |
| cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:* | 18.04 | Vulnerable | Canonical |
| cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:* | 20.04 | Vulnerable | Canonical |
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions before 5.4.101; 5.5.0 to before 5.10.19; 5.11 to before 5.11.2 Vulnerable ·Linux
- cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* Versions 9.0 Vulnerable ·Debian
- cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:esm:*:*:* Versions 14.04 Vulnerable ·Canonical
- cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:* Versions 16.04 Vulnerable ·Canonical
- cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:* Versions 18.04 Vulnerable ·Canonical
- cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:* Versions 20.04 Vulnerable ·Canonical
Remediation
- Fix · CNA kernel (Linux) Fixed in 5.12-rc1, 5.11.2, 5.10.19, 5.4.101
Red Hat 1 advisory
- RHSA-2021:4356 Released 2021-11-09 · Red Hat rating Moderatekernel security, bug fix, and enhancement update
- Red Hat CodeReady Linux Builder (v. 8) kernel-tools-libs-devel-4.18.0-348.el8
- Red Hat Enterprise Linux BaseOS (v. 8) bpftool-4.18.0-348.el8, kernel-4.18.0-348.el8, kernel-abi-stablelists-4.18.0-348.el8 +19
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 8 | Affected | No fix yet |
| Red Hat CodeReady Linux Builder (v. 8) | Fixed | RHSA-2021:4356 |
| Red Hat Enterprise Linux BaseOS (v. 8) | Fixed | RHSA-2021:4356 |
Not affected: 3 products
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 9
Timeline
- 2026-10-02 Threatist record created from CVE-2021-3444
- 2026-10-03 Alias added: GHSA-c55x-85rg-x529
References
Advisory 6
- https://www.openwall.com/lists/oss-security/2021/03/23/2
- [oss-security] 20210323 [CVE-2021-3444] Linux kernel bpf verifier incorrect mod32 truncation
- http://packetstormsecurity.com/files/162117/Kernel-Live-Patch-Security-Notice-LSN-0075-1.html
- https://security.netapp.com/advisory/ntap-20210416-0006/
- [debian-lts-announce] 20211015 [SECURITY] [DLA 2785-1] linux-4.19 security update
- http://packetstormsecurity.com/files/164950/Kernel-Live-Patch-Security-Notice-LSN-0082-1.html
More Linux Kernel vulnerabilities
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- TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
- TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
- TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
- TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
Sources
- CVE-2021-3444 · CVE Program
- CVE-2021-3444 · NVD
- FIRST EPSS
- GHSA-c55x-85rg-x529 · GitHub Advisory Database · CC BY 4.0
- CVE-2021-3444 · Red Hat security data · CC BY 4.0
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