North Korean APT InkySquid Infects Victims Using Browser Exploits
On another occasion, CVE-2021-26411 was used, which is another exploit targeting Internet Explorer and legacy versions of Microsoft Edge.
CVE-2021-26411 KEVRansomwarePublic exploit High · 8.8 EPSS 81.7%
Microsoft Internet Explorer Memory Corruption Vulnerability
Microsoft · Internet Explorer
Summary
A memory corruption flaw in Microsoft Internet Explorer, classified as a use-after-free issue, lives in the browser's rendering and memory-handling code. An attacker who can reach the target over the network can exploit it without authentication or special privileges, but a user must interact with the attacker's content, such as by visiting a malicious page, for the exploit to succeed, and the attack can affect resources beyond the vulnerable component's own security scope.
Official description · NVD
Internet Explorer Memory Corruption Vulnerability
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
83.0 / 100
- Exploited
- Yes, in CISA KEV
- Reports
- 1
- Tactics
- 1/15
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.How attackers get in
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 2 days before it was disclosed. Public exploit code (PoC-in-GitHub) appeared 8 months after disclosure.
- First seen exploitedVulnCheck KEV evidence2 days before
- Disclosedday 0
- Named in a threat reportvolexity.com+5 mo
- Added to CISA KEVknown ransomware use; EU database agrees+8 mo
- Public exploit codePoC-in-GitHub+8 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
1 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, 1 cited passage 1Initial 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
browser memory corruption via drive-by content
Internet Explorer Memory Corruption Vulnerability
Detection
0 rules for this CVE · 3 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-2021-26411 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
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Named in 1 threat report1 reportVolexityAug 2021
Reports are matched by finding the exact id CVE-2021-26411 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