CVE-2020-9859Known exploitationPublic exploit

Kernel code execution via lio_listio double free

Published Jun 5, 2020 · Updated Oct 21, 2025

Double-free memory corruption in Apple iOS, macOS, tvOS, and watchOS allows local users to execute code with kernel privileges. A race in XNU's lio_listio() handling frees the same lio_context twice, leaving a dangling allocation that an application can reclaim and use after free. Execution starts from a local application and can escape its sandbox with kernel privileges; public unc0ver 5.0 code exploited the flaw on iOS.

CVSS severity7.8
High
EPSS probability0.83%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double-free memory corruption in Apple iOS, macOS, tvOS, and watchOS allows local users to execute code with kernel privileges. A race in XNU's lio_listio() handling frees the same lio_context twice, leaving a dangling allocation that an application can reclaim and use after free. Execution starts from a local application and can escape its sandbox with kernel privileges; public unc0ver 5.0 code exploited the flaw on iOS.

The record

CVE
CVE-2020-9859
Published
Jun 5, 2020
Updated
Oct 21, 2025
Vendor
Apple
Product
iOS
Classifications
CWE-415, T1404, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 5, 2020CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2021Exploitation reportedCISA Known Exploited Vulnerabilities catalog listing
  3. Oct 21, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <iOS 13.5.1 and iPadOS 13.5.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Apple · iOSversion=unspecified <iOS 13.5.1 and iPadOS 13.5.1
Apple · tvOSversion=unspecified <tvOS 13.4.6
Apple · macOSversion=unspecified <macOS Catalina 10.15.5 Supplemental Update
Apple · watchOSversion=unspecified <watchOS 6.2.6

Published CVSS scores

7.8CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-415Double Free
T1404Exploitation for Privilege Escalation
T1068Exploitation for Privilege Escalation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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