HOMEVULNERABILITIESCVE-2021-28691
HIGH

CVE-2021-28691

CWE-416Published: June 29, 2021· Updated: Jun 17, 2026

7.8
CVSS v3.1

Official Description

Guest triggered use-after-free in Linux xen-netback A malicious or buggy network PV frontend can force Linux netback to disable the interface and terminate the receive kernel thread associated with queue 0 in response to the frontend sending a malformed packet. Such kernel thread termination will lead to a use-after-free in Linux netback when the backend is destroyed, as the kernel thread associated with queue 0 will have already exited and thus the call to kthread_stop will be performed against a stale pointer.

NVD Source

Technical Analysis

CVE-2021-28691 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 7.8.

From a weakness classification perspective (CWE-416): Use-after-free vulnerabilities involve accessing memory after it has been freed, often enabling arbitrary code execution.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorLocal
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

Linux1 product(s)
linux kernel
netapp17 product(s)
cloud backuph410c firmwareh410ch300s firmwareh300sh500s firmwareh500sh700s firmwareh700sh300e firmwareh300eh500e firmware+5
Source: NVD CPE · 18 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://security.gentoo.org/glsa/202107-30
ADVISORYhttps://security.netapp.com/advisory/ntap-20210805-0002/
ADVISORYhttps://xenbits.xenproject.org/xsa/advisory-374.txt
ADVISORYhttps://security.gentoo.org/glsa/202107-30
ADVISORYhttps://security.netapp.com/advisory/ntap-20210805-0002/
ADVISORYhttps://xenbits.xenproject.org/xsa/advisory-374.txt

All References (6)

→
https://security.gentoo.org/glsa/202107-30Third Party Advisory
→
https://security.netapp.com/advisory/ntap-20210805-0002/Third Party Advisory
→
https://xenbits.xenproject.org/xsa/advisory-374.txtThird Party Advisory
→
https://security.gentoo.org/glsa/202107-30Third Party Advisory
→
https://security.netapp.com/advisory/ntap-20210805-0002/Third Party Advisory
→
https://xenbits.xenproject.org/xsa/advisory-374.txtThird Party Advisory

Quick Facts

CVE IDCVE-2021-28691
CVSS Score7.8 / 10
SeverityHIGH
WeaknessCWE-416
CISA KEVNo
Affected2 vendor(s)
PublishedJun 29, 2021

Related CVEs (CWE-416)

CVE-2012-1972
10.0
CVE-2010-3252
10.0
CVE-2010-2302
10.0
CVE-2011-0982
10.0
CVE-2010-3116
10.0
CVE-2012-1973
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-28691 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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