CyberSecBulletin
CVE-2021-30952Exploited in the wildNVD status: Analyzed

Apple Multiple Products Integer Overflow or Wraparound

Published Updated By the CyberSecBulletin desk

CVE-2021-30952 is a high-severity integer overflow or wraparound vulnerability in watchOS 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 unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists version 8.3 as the first without the flaw, so updating watchOS to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on March 5, 2026, 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 watchOS to 8.3 or a later version.
  2. Update iOS and iPadOS to 15.2 or a later version.
  3. Update macOS to 12.1 or 15.2, whichever matches your release line, or a later version.
  4. CISA's required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
  5. Read the advisory on support.apple.com for workarounds and exact fixed builds.
  6. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
ApplewatchOSbefore 8.38.3
AppleiOS and iPadOSbefore 15.215.2
ApplemacOSbefore 12.1; before 15.212.1, 15.2
AppleSafaribefore 15.215.2
AppleiPadOSbefore 15.215.2
AppleIphone OSbefore 15.215.2
AppletvOSbefore 15.215.2
Fedora ProjectFedora34; 35Not stated
DebianDebian Linux10.0; 11.0Not stated
WebkitgtkWebkitgtkbefore 2.34.42.34.4
WpewebkitWpe Webkitbefore 2.34.42.34.4

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
NoneNo account or login is needed.
User interaction
RequiredA user must take an action such as opening a file or link.
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:N/UI:R/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.8HighNVD
CVSS 3.18.8HighCISA (ADP)
CVSS 2.06.8MediumNVD

Official description

An integer overflow was addressed with improved input validation. This issue is fixed in tvOS 15.2, macOS Monterey 12.1, Safari 15.2, iOS 15.2 and iPadOS 15.2, watchOS 8.3. Processing maliciously crafted web content may lead to arbitrary code execution.

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

The underlying weakness: Integer Overflow or Wraparound

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

How developers prevent this class of flaw

  • Ensure that all protocols are strictly defined, such that all out-of-bounds behavior can be identified simply, and require strict conformance to the protocol.
  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. If possible, choose a language or compiler that performs automatic bounds checking.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Use libraries or frameworks that make it easier to handle numbers without unexpected consequences. Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++).

More Integer Overflow or Wraparound vulnerabilities (CWE-190)

Timeline

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

References

Third-party and government advisories

Technical write-ups (may include proof of concept)

Other vulnerabilities in watchOS

All watchOS vulnerabilities

Recent Integer Overflow or Wraparound vulnerabilities

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