NVD / CVE Program· CNA Linux

CVE-2021-47541: net/mlx4_en: Fix an use-after-free bug in mlx4_en_try_alloc_resources()

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: 0.29% (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 Linux 676dc7d9b15bf8733233a2db1ec3f9091ab34275, 75917372eef0dbfb290ae45474314d35f97aea18, addad7643142f500080417dd7272f49b7a185570.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 676dc7d9b15bf8733233a2db1ec3f9091ab34275, 75917372eef0dbfb290ae45474314d35f97aea18, addad7643142f500080417dd7272f49b7a185570 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 the Linux kernel, the following vulnerability has been resolved: net/mlx4_en: Fix an use-after-free bug in mlx4_en_try_alloc_resources() In mlx4_en_try_alloc_resources(), mlx4_en_copy_priv() is called and tmp->tx_cq will be freed on the error path of mlx4_en_copy_priv(). After that mlx4_en_alloc_resources() is called and there is a dereference of &tmp->tx_cq[t][i] in mlx4_en_alloc_resources(), which could lead to a use after free problem on failure of mlx4_en_copy_priv(). Fix this bug by adding a check of mlx4_en_copy_priv() This bug was found by a static analyzer. The analysis employs differential checking to identify inconsistent security operations (e.g., checks or kfrees) between two code paths and confirms that the inconsistent operations are not recovered in the current function or the callers, so they constitute bugs. Note that, as a bug found by static analysis, it can be a false positive or hard to trigger. Multiple researchers have cross-reviewed the bug. Builds with CONFIG_MLX4_EN=m show no new warnings, and our static analyzer no longer warns about this code.

HighCVSS 7.8 · v3.1—No exploit Fix available

Memory safety

BDU:2024-04569

Published: May 24, 2024
Updated: Aug 5, 2026
EPSS: 0.2% · 22th percentile
CWE: CWE-416

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 31 / 40 · 7.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.2%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 7.8
CNA · Linux: 7.8; agree

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.

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Affected 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

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

linux linux kernel4.7 and later · before 4.14.257
linux linux kernel4.15 and later · before 4.19.220
linux linux kernel4.20 and later · before 5.4.164
linux linux kernel5.5 and later · before 5.10.84
linux linux kernel5.11 and later · before 5.15.7

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

Linux Linux
- 4.7affected
- ec25bc04ed8e12947738468cbe2191f1529f9e39 and later · before be12572c5ddc8ad7453bada4eec8fa46967dc757affected · git
- ec25bc04ed8e12947738468cbe2191f1529f9e39 and later · before 676dc7d9b15bf8733233a2db1ec3f9091ab34275affected · git
- ec25bc04ed8e12947738468cbe2191f1529f9e39 and later · before e461a9816a1ac5b4aeb61621b817225b61e46a68affected · git
- ec25bc04ed8e12947738468cbe2191f1529f9e39 and later · before f1d43efa59f1edd3e7eca0e94559b4c6b1cd4e2baffected · git
- ec25bc04ed8e12947738468cbe2191f1529f9e39 and later · before 75917372eef0dbfb290ae45474314d35f97aea18affected · git
- ec25bc04ed8e12947738468cbe2191f1529f9e39 and later · before addad7643142f500080417dd7272f49b7a185570affected · git
- before 4.7not affected · semver
- 4.14.257 and later · up to and including 4.14.*not affected · semver
- 4.19.220 and later · up to and including 4.19.*not affected · semver

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 5.15.15-1	5.15.15-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
90Now
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 KEV
89Now
CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
85Now

Published before and after this one in the same product

← EarlierCVE-2021-47539May 24, 2024 · rxrpc: Fix rxrpc_peer leak in rxrpc_look_up_bundle()
22Monitor
← EarlierCVE-2021-47540May 24, 2024 · mt76: mt7915: fix NULL pointer dereference in mt7915_get_phy_mode
22Monitor
Later →CVE-2021-47542May 24, 2024 · net: qlogic: qlcnic: Fix a NULL pointer dereference in qlcnic_83xx_add_rings()
22Monitor

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
Linux Linux	676dc7d9b15bf8733233a2db1ec3f9091ab34275	Vendor (CNA)
Linux Linux	75917372eef0dbfb290ae45474314d35f97aea18	Vendor (CNA)
Linux Linux	addad7643142f500080417dd7272f49b7a185570	Vendor (CNA)
Linux Linux	be12572c5ddc8ad7453bada4eec8fa46967dc757	Vendor (CNA)
Linux Linux	e461a9816a1ac5b4aeb61621b817225b61e46a68	Vendor (CNA)
Linux Linux	f1d43efa59f1edd3e7eca0e94559b4c6b1cd4e2b	Vendor (CNA)
debian:linux	5.15.15-1 · Debian:12	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.

No commit or PR link among the references.

Credits

All researchers

Finders, 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).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-24-0551 · May 27, 2024(Linux Kernel Güncellemesi)

All national notices →

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-416 · Use After Free

CVSS vector

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

nvd-primary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

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✗ → ✓Sep 28, 2026, 10:11 PM UTC

For records you follow, these changes also arrive as notifications. →

References

git.kernel.org/stable/c/676dc7d9b15bf8733233a2db1ec3f9091ab34275

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records