CVE-2010-0249: Microsoft Internet Explorer Use-After-Free 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 2026-05-20, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-06-03; treat that as the outer limit, not the target.
• EPSS 91.9%, percentile 99.8: FIRST’s model estimates a 91.9% chance of exploitation activity in the next 30 days, higher than 99.8% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.

What it is

Use-after-free vulnerability in Microsoft Internet Explorer 6, 6 SP1, 7, and 8 on Windows 2000 SP4; Windows XP SP2 and SP3; Windows Server 2003 SP2; Windows Vista Gold, SP1, and SP2; Windows Server 2008 Gold, SP2, and R2; and Windows 7 allows remote attackers to execute arbitrary code by accessing a pointer associated with a deleted object, related to incorrectly initialized memory and improper handling of objects in memory, as exploited in the wild in December 2009 and January 2010 during Operation Aurora, aka "HTML Object Memory Corruption Vulnerability."

CISA’s summary

Microsoft Internet Explorer contains an use-after-free vulnerability that could allow remote attackers to execute arbitrary code by accessing a pointer associated with a deleted object. 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: 2010-01-15

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: required (a user must click/open something)
• 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 2026-05-20; federal due date 2026-06-03. 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 no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 91.94% probability of exploitation activity in the next 30 days; percentile 99.8.

Timeline

• 2010-01-15 — CVE record published by microsoft
• 2026-05-20 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2026-05-21 — CVE record last updated
• 2026-06-03 — 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. 979352 support.microsoft.com
2. MS10-002 docs.microsoft.com
3. Listed in CISA KEV notes (learn.microsoft.com) learn.microsoft.com

Vulnerability records

1. CVE.org record CVE-2010-0249 cve.org
2. NVD entry CVE-2010-0249 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

1. microsoft.com microsoft.com
2. oval:org.mitre.oval:def:6835 oval.cisecurity.org
3. 61697 osvdb.org
4. 37815 securityfocus.com
5. VU#492515 kb.cert.org
6. 11167 exploit-db.com
7. blogs.technet.com blogs.technet.com
8. ie-freed-object-code-execution(55642) exchange.xforce.ibmcloud.com
9. TA10-055A us-cert.gov
10. news.cnet.com news.cnet.com
11. 1023462 securitytracker.com
12. ADV-2010-0135 vupen.com

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