Objective-See's Blog OSX.CDDS (OSX.MacMa)
A webkit “n-day” RCE (patched as CVE-2021-1789 in January)
CVE-2021-1789 KEV High · 8.8 EPSS 14.0%
Apple Multiple Products Type Confusion Vulnerability
Apple · Multiple Products
Summary
The flaw is a type confusion vulnerability in multiple Apple products, addressed through improved state handling, affecting macOS Big Sur, macOS Catalina and Mojave security updates, tvOS, watchOS, iOS, iPadOS and Safari. An attacker can achieve arbitrary code execution by getting a user to process maliciously crafted web content, requiring network access and user interaction with no prior authentication.
Official description · NVD
A type confusion issue was addressed with improved state handling. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, tvOS 14.4, watchOS 7.3, iOS 14.4 and iPadOS 14.4, Safari 14.0.3. Processing maliciously crafted web content may lead to arbitrary code execution.
Priority scorePatchfirst’s 0 to 100 ranking. It adds points for CISA KEV listing, ransomware use, EPSS, threat reports, public exploit code and CVSS. Every CVE page shows the breakdown. Breakdown
67.3 / 100
- Exploited
- Yes, in CISA KEV
- Reports
- 1
- Tactics
- 2/15
How an attack unfolds
Based on MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. mappings. Select a step to see the evidence.Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited 6 months after disclosure.
- Disclosedday 0
- First seen exploitedVulnCheck KEV evidence+6 mo
- Added to CISA KEVEU database agrees+13 mo
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
2 TechniqueOne specific attacker behaviour in MITRE ATT&CK, such as T1190 “Exploit Public-Facing Application”. IDs with a dot, like T1059.004, are sub-techniques., grouped by TacticThe attacker’s goal at a stage of an attack in MITRE ATT&CK, such as Initial Access or Persistence. Each technique belongs to one or more tactics. in kill-chain order, 2 cited passages 2Initial AccessTA0001
Drive-by Compromise T1189 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
AI mapping from the description · how it is exploited
Malicious web content delivered to victim browsers
Processing maliciously crafted web content may lead to arbitrary code execution
ExecutionTA0002
Command and Scripting Interpreter T1059 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
AI mapping from the description · primary impact
Direct arbitrary code execution from processing content
may lead to arbitrary code execution
Detection
0 rules for this CVE · 98 general rules for its techniquesRules for this CVE
0Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2021-1789 directly.CVE-specific rules are not available in this build. Search SigmaHQ ↗
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
Drive-by CompromiseT11893 general rules
Command and Scripting InterpreterT105995 general rules
- HackTool - Sliver C2 Implant Activity Patterncriticaltest
- Lazarus Group Activitycriticaltest
- REvil Kaseya Incident Malware Patternscriticaltest
- Turla Group Lateral Movementcriticaltest
- Windows Defender AMSI Trigger Detectedhighstable
- Windows Defender Threat Detectedhighstable
- Abusable DLL Potential Sideloading From Suspicious Locationhightest
- Add Insecure Download Source To Wingethightest
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Named in 1 threat report1 reportobjective-see.org
Reports are matched by finding the exact id CVE-2021-1789 in their text; nobody has reviewed the match. One passage is shown per report, at most 320 characters, linked to the original.
Also mentioned in 50 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Actively_Exploited_Kev | Oct 29, 202628 Oct 2026
- Actively_Exploited_Kev | Oct 28, 202627 Oct 2026
- Actively_Exploited_Kev | Oct 27, 202626 Oct 2026
- Actively_Exploited_Kev | Oct 24, 202623 Oct 2026
- Actively_Exploited_Kev | Oct 23, 202622 Oct 2026
- Actively_Exploited_Kev | Oct 22, 202621 Oct 2026
- 44 more on OTX