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CVE-2021-4135

21
FAUCET Score

CVE-2021-4135 is a medium-severity memory leak vulnerability affecting the Linux kernel, specifically within the eBPF for the Simulated networking device driver. A local attacker could exploit this flaw by leveraging the nsim_map_alloc_elem function to gain unauthorized access to sensitive data. The vulnerability has a CVSS score of 5.5 (Medium) with a local attack vector and low attack complexity, leading to high confidentiality impact. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 5.16CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
5.16CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:5.16:-:*:*:*:*:*:*
5.16CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:*
5.16CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:*
5.16CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.5MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
1.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.23%
Probability of exploitation in next 30 days
EPSS Percentile
14.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0023 is in the 63rd percentile among its peer group of 15,940 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (7)

microsoftpatch availablevia msrc
Product: 18617-16823Fixed in: 5.15.67.1-4
microsoftpatch availablevia msrc
Product: cm1 kernel 5.10.134.1-2 on CBL Mariner 1.0Fixed in: 5.10.134.1-2
microsoftpatch availablevia msrc
Product: cbl2 kernel 5.15.67.1-4 on CBL Mariner 2.0Fixed in: 5.15.67.1-4
microsoftpatch availablevia msrc
Product: 18638-16820Fixed in: 5.10.134.1-2
redhatno patchvia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: kernel-rt
redhatno patchvia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: kernel
redhatno patchvia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: kernel

Vendor Advisories (2)

microsoft2022-Jul/CVE-2021-4135Moderate

A memory leak vulnerability was found in the Linux kernel's eBPF for the Simulated networking device driver in the way user uses BPF for the device such that function nsim_map_alloc_elem being called. A local user could use this flaw to get unauthorized access to some data.

Jul 12, 2022
redhatCVE-2021-4135Moderate

kernel: Heap information leak in map_lookup_elem function

Dec 15, 2021

References

git.kernel.org / pub/scm/linux/kernel/git/netdev/net.git/commit
Mailing ListPatchVendor Advisory