Vulnerability record · CVE-2006-1993 · published 25 April 2006
CVE-2006-1993: Firefox designMode iframe focus use-after-free allows code execution
Mozilla · Firefox
Mozilla Firefox 1.5.0.2 mishandles the contentWindow.focus method on an iframe when designMode is enabled, leaving a reference to a deleted controller context object. This use-after-free can crash the browser and may allow arbitrary code execution. The vendor disputes the original claim that this was a buffer overflow in js320.dll or xpcom_core.dll.
Description
Mozilla Firefox 1.5.0.2, when designMode is enabled, allows remote attackers to cause a denial of service and possibly execute arbitrary code via certain Javascript that is not properly handled by the contentWindow.focus method in an iframe, which causes a reference to a deleted controller context object. NOTE: this was originally claimed to be a buffer overflow in (1) js320.dll and (2) xpcom_core.dll, but the vendor disputes this claim.
AV:N/AC:H/Au:N/C:P/I:P/A:P
Automated analysis
medium priorityCVSS 2.0 score is 5.1 (medium) and the product is long end-of-life, but public exploit references and a high EPSS percentile raise concern for unpatched legacy systems.
What it is
Mozilla Firefox 1.5.0.2 mishandles the contentWindow.focus method on an iframe when designMode is enabled, leaving a reference to a deleted controller context object. This use-after-free can crash the browser and may allow arbitrary code execution. The vendor disputes the original claim that this was a buffer overflow in js320.dll or xpcom_core.dll.
Impact
An attacker can cause a denial of service and possibly execute arbitrary code in the context of the browser. The CVSS 2.0 vector rates partial confidentiality, integrity and availability impact.
Attack surface
Reached remotely over the network by loading crafted JavaScript in a page that uses an iframe with designMode enabled. No authentication is required, but the high attack complexity and the need for the victim to view the malicious content imply some user interaction.
Exploitation
Not listed in CISA KEV, but EPSS is 0.54003 (98.95th percentile) and multiple references are tagged Exploit, indicating public exploit code exists.
What to do
- Upgrade Firefox to a version containing the vendor fix referenced in MFSA 2006-30 and the Secunia patch advisory.
- Apply the Debian, Gentoo or other distribution security updates for the affected Firefox packages.
- Disable JavaScript or restrict script execution for untrusted sites where feasible.
- Consider disabling designMode-dependent content or isolating browsing of untrusted pages.
Detection
- Monitor browser crash reports for Firefox 1.5.0.2 crashes involving iframe focus or designMode.
- Search proxy or network logs for known exploit URLs from the referenced securitytracker, securident and SecurityFocus exploit postings.
- Use endpoint detection to flag Firefox processes spawning unexpected child processes or exhibiting memory corruption behavior.
This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.
Affected products
1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.
References
Track CVE-2006-1993 inside VULONE
Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.
Related vulnerabilities
Same products first, then exploited flaws of the same weakness class.
Source: NIST National Vulnerability Database (record CVE-2006-1993), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.
