CVE-2021-0920

In unix_scm_to_skb of af_unix.c, there is a possible use after free bug due to a race condition. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-196926917References: Upstream kernel

CVSS: 6.4Mediumscored by CISA
Exploited in the wild: Yes, in CISA KEV since 23 May 2022CISA deadline for US federal agencies: 13 Jun 2022
EPSS: 0.87%chance of exploitation in the next 30 daystop 41% of scored CVEsFIRST score of 11 Nov 2026
Fix: Patch availablesee the advisories in the references
Published: 15 Dec 2021analysed here 12 Nov 2026

Do first. Apply updates per vendor instructions. (CISA's required action for this KEV entry)

Summary

Triage

Attack surface: Server-side
Exploitable: At runtime
Attack vector: local
Weaknesses: CWE-362 Common Weakness
CWE-416 Use After Free
Can a WAF block it?: No. See why

The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.

Affected products

Product	Affected versions	Vendor says fixed in
Android	Android kernelVendor says fixed in: not stated	Not stated by the vendor

As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.

Products named in our analysis

linux:linux_kernel
google:android
debian:debian_linux

Fix and mitigation

WAF and other mitigations

Can a WAF block it? No. The attack needs local access to the machine, so a WAF is not on its path.

Also consider: patch

Based on the attack vector (local or physical access). We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.

Remediation steps (AI-written)

Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.

Exploitation evidence

CISA KEV catalog: Listed since 23 May 2022.
CISA due date: 13 Jun 2022, the remediation deadline for US federal agencies
CISA required action: Apply updates per vendor instructions.
Public exploit code: None on record in Exploit-DB, Metasploit, Nuclei templates or PoC-in-GitHub.
CISA SSVC: exploitation active, automatable no, technical impact totalAssessed by CISA 6 Feb 2024 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.

Timeline

15 Dec 2021Published
23 May 2022Added to CISA KEV (exploited in the wild)158 days (about 5 months) later
13 Jun 2022CISA remediation due date (US federal agencies)21 days later
6 Feb 2024CISA SSVC assessment: exploitation active604 days (about 2 years) later
21 Oct 2025CVE record last updated623 days (about 2 years) later
12 Nov 2026Analysed by vulneraibility.com387 days (about 1 year) later

CVSS vector

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

Metric	Value	What it means
Attack vector	LocalLocal access required (shell, logged-in user).	Local access required (shell, logged-in user).
Attack complexity	HighNeeds specific conditions, a race or a particular configuration.	Needs specific conditions, a race or a particular configuration.
Privileges required	HighThe attacker needs admin-level privileges.	The attacker needs admin-level privileges.
User interaction	NoneNo victim action needed.	No victim action needed.
Scope	UnchangedImpact stays within the vulnerable component.	Impact stays within the vulnerable component.
Confidentiality	HighTotal data disclosure possible.	Total data disclosure possible.
Integrity	HighComplete modification possible.	Complete modification possible.
Availability	HighFull outage possible.	Full outage possible.

Common questions

Is CVE-2021-0920 being exploited?

Yes. CVE-2021-0920 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.

How severe is CVE-2021-0920?

CVE-2021-0920 is rated Medium with a CVSS score of 6.4. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2021-0920?

Yes. A fix has been recorded for CVE-2021-0920. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2021-0920 affect?

CVE-2021-0920 affects linux:linux_kernel, google:android, debian:debian_linux. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

References

NVD CVE.org CVE Details Source

3 references in the CVE record, grouped by the tags the record gives them.

Where the data on this page comes from

CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
NVD: CVSS and CPE data
CISA KEV catalog: exploitation, date added, due date
CISA Vulnrichment (ADP): SSVC decision points
FIRST EPSS: exploit probability and percentile

Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.

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