CVE-2010-3962: Microsoft Internet Explorer Uninitialized Memory Corruption Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Microsoft Internet Explorer. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-10-06, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-10-27; treat that as the outer limit, not the target.
• EPSS 96.8%, percentile 99.9: FIRST’s model estimates a 96.8% chance of exploitation activity in the next 30 days, higher than 99.9% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.

What it is

Use-after-free vulnerability in Microsoft Internet Explorer 6, 7, and 8 allows remote attackers to execute arbitrary code via vectors related to Cascading Style Sheets (CSS) token sequences and the clip attribute, aka an "invalid flag reference" issue or "Uninitialized Memory Corruption Vulnerability," as exploited in the wild in November 2010.

CISA’s summary

Microsoft Internet Explorer contains an uninitialized memory corruption vulnerability that could allow for remote code execution. The impacted product could be end-of-life (EoL) and/or end-of-service (EoS). Users should discontinue product utilization.

Weakness type: CWE-416.

Product: Microsoft Internet Explorer · Assigned by: microsoft · Published: 2010-11-05

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: high (needs special conditions)
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2025-10-06; federal due date 2025-10-27. Known ransomware use: Unknown.
• CISA 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.
• CISA SSVC assessment: exploitation active, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 96.83% probability of exploitation activity in the next 30 days; percentile 99.9.

Timeline

• 2010-11-05 — CVE record published by microsoft
• 2025-10-06 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2025-10-22 — CVE record last updated
• 2025-10-27 — CISA remediation deadline for US federal agencies

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. MS10-090 docs.microsoft.com
2. Listed in CISA KEV notes (learn.microsoft.com) learn.microsoft.com

Vulnerability records

1. CVE.org record CVE-2010-3962 cve.org
2. NVD entry CVE-2010-3962 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

1. 44536 securityfocus.com
2. TA10-348A us-cert.gov
3. VU#899748 kb.cert.org
4. 42091 secunia.com
5. ADV-2010-2880 vupen.com
6. microsoft.com microsoft.com
7. 1024676 securitytracker.com
8. 15421 exploit-db.com
9. symantec.com symantec.com
10. ms-ie-flag-code-execution(62962) exchange.xforce.ibmcloud.com
11. blogs.technet.com blogs.technet.com
12. oval:org.mitre.oval:def:12279 oval.cisecurity.org
13. 15418 exploit-db.com

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