CVE-2021-28691: linux Use After Free
Vulnerability summary
CVE-2021-28691 is a high (CVSS 7.8) Use After Free vulnerability in linux. EPSS estimates a 0.36% chance of exploitation in the next 30 days, higher than 30.3% of scored vulnerabilities.
Not severe (CVSS 7.8, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 5 · Related 3Timeline
- 29-06-2021PublishedVulnerability first disclosed.
- 03-08-2024Last modifiedVulnerability information updated.
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.
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.36%
Chance of exploitation in the next 30 days
Percentile
30%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.36% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu30 products
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11< 5.11.0-1016.17~20.04.1
- linux-aws-5.3All versions (No fix recorded)
- linux-aws-5.8< 5.8.0-1042.44~20.04.1
- linux-azureAll versions (No fix recorded)
Linux2 products
- linux≥ 5.5.0, < unspecified
- linux_kernel≥ 5.5.0, < 5.10.43
Debian1 product
- linux< 5.10.46-1
4 vendors · 43 products
