CVE-2021-33624: In kernel/bpf/verifier.c in the Linux kernel before 5.12.13, a branch can be mispredicted (e.g., because of type confusion) and consequently
Noroxi assessment
Priority: Monitor (action score 18/100)
- Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.93% (FIRST EPSS); higher than 60.8% of all records.
- Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
- Fixed version: linux (Debian:12) 5.10.46-1; linux-4.19 (Debian:9) 4.19.208-1~deb9u1; kernel-64kb (openSUSE:Leap 15.3) 5.3.18-59.13.1.
Low priority for now. Upgrade to linux (Debian:12) 5.10.46-1; linux-4.19 (Debian:9) 4.19.208-1~deb9u1; kernel-64kb (openSUSE:Leap 15.3) 5.3.18-59.13.1 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
In kernel/bpf/verifier.c in the Linux kernel before 5.12.13, a branch can be mispredicted (e.g., because of type confusion) and consequently an unprivileged BPF program can read arbitrary memory locations via a side-channel attack, aka CID-9183671af6db.
- BDU:2021-03232
- DLA-2785-1
- openSUSE-SU-2021:2305-1
- openSUSE-SU-2021:2352-1
- openSUSE-SU-2021:2427-1
- SUSE-SU-2021:2303-1
- SUSE-SU-2021:2305-1
- SUSE-SU-2021:2321-1
- SUSE-SU-2021:2324-1
- SUSE-SU-2021:2325-1
- SUSE-SU-2021:2349-1
- SUSE-SU-2021:2352-1
- SUSE-SU-2021:2421-1
- SUSE-SU-2021:2422-1
- SUSE-SU-2021:2426-1
- SUSE-SU-2021:2427-1
- Published
- Jun 23, 2021
- Updated
- Oct 8, 2026
- EPSS
- 0.9% · 60th percentile
- CWE
- CWE-843
Report tools
Action score
18
Monitor
Low priority for now.
- CVSS
- 18 / 40 · 4.7 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.9%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- Proof of concept exists, no weaponized module
- 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 |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- debian debian linux9.0
- linux linux kernelbefore 5.12.13
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 5.10.46-1 | 5.10.46-1 |
| Debian:9 | linux-4.19 | before 4.19.208-1~deb9u1 | 4.19.208-1~deb9u1 |
| openSUSE:Leap 15.3 | kernel-64kb | before 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| openSUSE:Leap 15.3 | kernel-azure | before 5.3.18-38.11.1 | 5.3.18-38.11.1 |
| openSUSE:Leap 15.3 | kernel-debug | before 4.12.14-197.99.1 | 4.12.14-197.99.1 |
| openSUSE:Leap 15.3 | kernel-debug | before 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| openSUSE:Leap 15.3 | kernel-default | before 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| 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 5.3.18-59.13.1.18.6.1 | 5.3.18-59.13.1.18.6.1 |
| openSUSE:Leap 15.3 | kernel-docs | before 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| 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 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| openSUSE:Leap 15.3 | kernel-obs-build | before 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| openSUSE:Leap 15.3 | kernel-obs-qa | before 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| openSUSE:Leap 15.3 | kernel-preempt | before 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| openSUSE:Leap 15.3 | kernel-source | before 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| openSUSE:Leap 15.3 | kernel-source-azure | before 5.3.18-38.11.1 | 5.3.18-38.11.1 |
| openSUSE:Leap 15.3 | kernel-syms | before 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| openSUSE:Leap 15.3 | kernel-syms-azure | before 5.3.18-38.11.1 | 5.3.18-38.11.1 |
| openSUSE:Leap 15.3 | kernel-vanilla | before 4.12.14-197.99.1 | 4.12.14-197.99.1 |
| openSUSE:Leap 15.3 | kernel-zfcpdump | before 4.12.14-197.99.1 | 4.12.14-197.99.1 |
| openSUSE:Leap 15.3 | kernel-zfcpdump | before 5.3.18-59.13.1 | 5.3.18-59.13.1 |
| SUSE:Linux Enterprise High Availability Extension 12 SP5 | kernel-default | before 4.12.14-122.77.1 | 4.12.14-122.77.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP1-ESPOS | kernel-docs | before 4.12.14-197.99.1 | 4.12.14-197.99.1 |
+60
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-2021-32078Jun 17, 2021 · An Out-of-Bounds Read was discovered in arch/arm/mach-footbridge/personal-pci.c in the Linux kernel through 5.12.11 because of the lack of a28Monitor
- ← EarlierCVE-2010-2525Jun 22, 2021 · A flaw was discovered in gfs2 file system’s handling of acls (access control lists).31Monitor
- Later →CVE-2020-28097Jun 24, 2021 · The vgacon subsystem in the Linux kernel before 5.8.10 mishandles software scrollback.23Monitor
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 | 5.10.46-1 · Debian:12 | Package registry (OSV) |
| debian:linux-4.19 | 4.19.208-1~deb9u1 · Debian:9 | Package registry (OSV) |
| opensuse:kernel-64kb | 5.3.18-59.13.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-azure | 5.3.18-38.11.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-debug | 5.3.18-59.13.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-default | 5.3.18-59.13.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-default-base | 5.3.18-59.13.1.18.6.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-docs | 5.3.18-59.13.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-kvmsmall | 5.3.18-59.13.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-obs-build | 5.3.18-59.13.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-obs-qa | 5.3.18-59.13.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-preempt | 5.3.18-59.13.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-source-azure | 5.3.18-38.11.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| opensuse:kernel-syms-azure | 5.3.18-38.11.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| suse:kernel-azure | 5.3.18-18.53.1 · SUSE:Linux Enterprise Module for Public Cloud 15 SP2 | Package registry (OSV) |
| suse:kernel-default | 4.12.14-122.77.1 · SUSE:Linux Enterprise High Availability Extension 12 SP5 | Package registry (OSV) |
| suse:kernel-default-base | 5.3.18-24.70.1.9.32.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP2 | Package registry (OSV) |
| suse:kernel-docs | 4.12.14-122.77.1 · SUSE:Linux Enterprise Software Development Kit 12 SP5 | Package registry (OSV) |
| suse:kernel-livepatch-SLE15-SP2_Update_16 | 1-5.3.1 · SUSE:Linux Enterprise Live Patching 15 SP2 | Package registry (OSV) |
| suse:kernel-obs-build | 4.12.14-122.77.1 · SUSE:Linux Enterprise Software Development Kit 12 SP5 | Package registry (OSV) |
| suse:kernel-preempt | 5.3.18-24.70.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP2 | Package registry (OSV) |
| suse:kernel-source | 4.12.14-122.77.1 · SUSE:Linux Enterprise Server 12 SP5 | Package registry (OSV) |
| suse:kernel-source-azure | 5.3.18-18.53.1 · SUSE:Linux Enterprise Module for Public Cloud 15 SP2 | Package registry (OSV) |
| suse:kernel-syms | 4.12.14-122.77.1 · SUSE:Linux Enterprise Server 12 SP5 | Package registry (OSV) |
| suse:kernel-syms-azure | 5.3.18-18.53.1 · SUSE:Linux Enterprise Module for Public Cloud 15 SP2 | Package registry (OSV) |
| suse:kgraft-patch-SLE12-SP5_Update_20 | 1-8.3.1 · SUSE:Linux Enterprise Live Patching 12 SP5 | Package registry (OSV) |
Exploit status
Proof of concept available
A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.
Evidence
- Proof-of-concept repository on GitHub ×1
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 |
|---|---|---|
| Proof-of-concept repository on GitHub | stars:4 | 2021-06-25 |
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.
- Published
- First PoC+1 d
- TodayNov 10, 2026+1966 d
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.
No credits in the CNA record.
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.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- high · data can be read
- Integrity
- none
- Availability
- none
- Attack vector
- Local
- Attack complexity
- High
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- None
- Availability impact
- None
Weakness class (CWE)
CWE-843 · Access of Resource Using Incompatible Type ('Type Confusion')CVSS vector
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
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
- SSVC exploitation— → none
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (3 more)Show less
Vendor advisories and official records. Exploit/PoC links are deliberately left out.