Apple Multiple Products WebKit Memory Corruption
CVE-2021-30665 is a high-severity out-of-bounds write vulnerability in macOS from Apple, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists versions 11.3, 14.5, 7.4 as the first without the flaw, so updating macOS to one of those releases 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.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update macOS to 11.3 or 14.5 or 7.4 or 12.5, whichever matches your release line, or a later version.
- Update iPadOS to 14.5.1 or a later version.
- Update Iphone OS to 12.5.3 or 14.5.1, whichever matches your release line, or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on support.apple.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
- 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
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apple | macOS | before 11.3; before 14.5; before 7.4; before 12.5; before 14.6 | 11.3, 14.5, 7.4, 12.5, 14.6 |
| Apple | iPadOS | before 14.5.1 | 14.5.1 |
| Apple | Iphone OS | before 12.5.3; 13.0 up to, but not including, 14.5.1 | 12.5.3, 14.5.1 |
| Apple | tvOS | before 14.6 | 14.6 |
| Apple | watchOS | before 7.4.1 | 7.4.1 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- 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:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.8 | High | NVD |
| CVSS 3.1 | 8.8 | High | CISA (ADP) |
| CVSS 2.0 | 6.8 | Medium | NVD |
Official description
A memory corruption issue was addressed with improved state management. This issue is fixed in watchOS 7.4.1, iOS 14.5.1 and iPadOS 14.5.1, tvOS 14.6, iOS 12.5.3, macOS Big Sur 11.3.1. Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- support.apple.com/en-us/HT212335Release Notes
- support.apple.com/en-us/HT212336Release Notes
- support.apple.com/en-us/HT212339Release Notes
- support.apple.com/en-us/HT212341Release Notes
- support.apple.com/en-us/HT212532Release Notes
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30665Third Party Advisory, US Government Resource
Other vulnerabilities in macOS
- 8.8 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
Recent Out-of-bounds Write vulnerabilities
- 8.8 High severity
Apple iOS WebKit Memory Corruption Exploited
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
- 10.0 Critical severity
SolarWinds Serv-U Remote Code Execution Exploited
- 7.8 High severity
Linux Kernel Heap Out-of-Bounds Write Exploited
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