How severe is CVE-2008-3843?

CVE-2008-3843 has a CVSS 2.0 base score of 4.3, rated medium severity.

Is CVE-2008-3843 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 22% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2008-3843?

CVE-2008-3843 primarily affects Microsoft .net Framework. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2008-3843?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2008-3843 published?

CVE-2008-3843 was published on 2008-08-27 and last updated on 2026-06-16.

CVE-2008-3843

CVE-2008-3843 is a medium-severity vulnerability in Microsoft .net Framework with a CVSS 2.0 base score of 4.3. Its EPSS exploit-prediction score of 22% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 2.0 base score 4.3)
EPSS exploit prediction: 22% (97th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Microsoft .net Framework
Published: 2008-08-27
Last modified: 2026-06-16

Description

Request Validation (aka the ValidateRequest filters) in ASP.NET in Microsoft .NET Framework with the MS07-040 update does not properly detect dangerous client input, which allows remote attackers to conduct cross-site scripting (XSS) attacks, as demonstrated by a query string containing a "<~/" (less-than tilde slash) sequence followed by a crafted STYLE element.

Frequently asked questions

What is CVE-2008-3843?: Request Validation (aka the ValidateRequest filters) in ASP.NET in Microsoft .NET Framework with the MS07-040 update does not properly detect dangerous client input, which allows remote attackers to conduct cross-site scripting (XSS) attacks, as demonstrated by a query string containing a "<~/" (less-than tilde slash) sequence followed by a crafted STYLE element.
How severe is CVE-2008-3843?: CVE-2008-3843 has a CVSS 2.0 base score of 4.3, rated medium severity.
Is CVE-2008-3843 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 22% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2008-3843?: CVE-2008-3843 primarily affects Microsoft .net Framework. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2008-3843?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2008-3843 published?: CVE-2008-3843 was published on 2008-08-27 and last updated on 2026-06-16.

References

Affected products (3)

cpe:2.3:a:microsoft:.net_framework:1.0:sp3:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:1.1:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:2.0:*:*:*:*:*:*:*

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