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» CVE-2021-26411
Internet Explorer Memory Corruption Vulnerability
NVD Status： Analyzed ，CVE State: published
Threat Intelligence & Risk Assessment for CVE-2021-26411
Conclusion & alert: CVE-2021-26411 is rated Critical Active Threat (95.2/100) : CVSS High severity, with high exploitation likelihood (EPSS 92.47%, 100th percentile).Core evidence: CISA KEV confirms active exploitation (added 2021-11-03) affecting Microsoft / Internet Explorer. a weakness (CWE-416) Unauthenticated remote administrative access may be possible.Mandatory action: The CISA remediation deadline has passed—treat as an emergency patch priority.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
CISA KEV Record for CVE-2021-26411
Name : Microsoft Internet Explorer Memory Corruption Vulnerability · CISA KEV detail
Exploit added : 2021-11-03
Action due : 2021-11-17
Required action : Apply updates per vendor instructions.
Exploit prediction scoring system (EPSS) score for CVE-2021-26411
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
#
Date
Old EPSS score
New EPSS score
Delta (New - Old)
1
2025-12-28
92.42%
92.47%
+0.06%
2
2025-12-27
92.47%
92.42%
-0.06%
3
2025-11-21
—
92.47%
—
Full EPSS history
(53 records total)
Common vulnerability scoring system (CVSS) metrics for CVE-2021-26411
CVSS metrics for this CVE.
Base score
Version
Severity
Vector
Exploitability
Impact
Score source
8.8
3.1
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L
Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
2.8
5.3
[email protected]
8.8
3.1
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
2.8
5.9
[email protected]
5.1
2.0
MEDIUM
AV:N/AC:H/Au:N/C:P/I:P/A:P
Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:H)
Exploitation requires uncommon or highly specific conditions.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
4.9
6.4
[email protected]
Weakness enumeration for CVE-2021-26411
Affected software / configurations for CVE-2021-26411
References for CVE-2021-26411
cvelogic
Threat Intelligence