CyberSecBulletin
CVE-2020-9859Exploited in the wildNVD status: Analyzed

Apple Multiple Products Code Execution

Published Updated By the CyberSecBulletin desk

CVE-2020-9859 is a high-severity double free vulnerability in iOS from Apple, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version iOS 13.5.1 and iPadOS 13.5.1 as the first without the flaw, so updating iOS to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update iOS to iOS 13.5.1 and iPadOS 13.5.1 or a later version.
  2. Update macOS to macOS Catalina 10.15.5 Supplemental Update or a later version.
  3. Update tvOS to tvOS 13.4.6 or a later version.
  4. CISA's required action: Apply updates per vendor instructions.
  5. Read the advisory on support.apple.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
AppleiOSbefore iOS 13.5.1 and iPadOS 13.5.1iOS 13.5.1 and iPadOS 13.5.1
ApplemacOSbefore macOS Catalina 10.15.5 Supplemental UpdatemacOS Catalina 10.15.5 Supplemental Update
AppletvOSbefore tvOS 13.4.6tvOS 13.4.6
ApplewatchOSbefore watchOS 6.2.6watchOS 6.2.6
AppleiPadOSbefore 13.5.113.5.1
AppleIphone OSbefore 13.5.113.5.1
AppleMac OS Xbefore 10.15.510.15.5

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.8HighNVD
CVSS 3.17.8HighCISA (ADP)
CVSS 2.07.2HighNVD

Official description

A memory consumption issue was addressed with improved memory handling. This issue is fixed in iOS 13.5.1 and iPadOS 13.5.1, macOS Catalina 10.15.5 Supplemental Update, tvOS 13.4.6, watchOS 6.2.6. An application may be able to execute arbitrary code with kernel privileges.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Double Free

The product calls free() twice on the same memory address.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.
  • Use a static analysis tool to find double free instances.

More Double Free vulnerabilities (CWE-415)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. Deadline for US federal agencies to remediate, set by CISA.
  4. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
  5. Record last changed materially (score, affected products, status or references).

References

Advisories

Third-party and government advisories

Other vulnerabilities in iOS

All iOS vulnerabilities

Recent Double Free vulnerabilities

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