How severe is CVE-2008-5531?

CVE-2008-5531 has a CVSS 2.0 base score of 9.3, rated critical severity.

Is CVE-2008-5531 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2008-5531?

CVE-2008-5531 affects Fortinet Fortiguard Antivirus. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2008-5531?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2008-5531 published?

CVE-2008-5531 was published on 2008-12-12 and last updated on 2026-06-16.

CVE-2008-5531

CVE-2008-5531 is a critical-severity vulnerability in Fortinet Fortiguard Antivirus with a CVSS 2.0 base score of 9.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: Critical (CVSS 2.0 base score 9.3)
EPSS exploit prediction: 3% (86th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Fortinet Fortiguard Antivirus
Published: 2008-12-12
Last modified: 2026-06-16

Description

Fortinet Antivirus 3.113.0.0, when Internet Explorer 6 or 7 is used, allows remote attackers to bypass detection of malware in an HTML document by placing an MZ header (aka "EXE info") at the beginning, and modifying the filename to have (1) no extension, (2) a .txt extension, or (3) a .jpg extension, as demonstrated by a document containing a CVE-2006-5745 exploit.

Frequently asked questions

What is CVE-2008-5531?: Fortinet Antivirus 3.113.0.0, when Internet Explorer 6 or 7 is used, allows remote attackers to bypass detection of malware in an HTML document by placing an MZ header (aka "EXE info") at the beginning, and modifying the filename to have (1) no extension, (2) a .txt extension, or (3) a .jpg extension, as demonstrated by a document containing a CVE-2006-5745 exploit.
How severe is CVE-2008-5531?: CVE-2008-5531 has a CVSS 2.0 base score of 9.3, rated critical severity.
Is CVE-2008-5531 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2008-5531?: CVE-2008-5531 affects Fortinet Fortiguard Antivirus. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2008-5531?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2008-5531 published?: CVE-2008-5531 was published on 2008-12-12 and last updated on 2026-06-16.

References

Affected products (1)

cpe:2.3:a:fortinet:fortiguard_antivirus:3.113.0.0:*:*:*:*:*:*:*

Other CWE-20 (Improper Input Validation) vulnerabilities

CVE-2026-48316 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48281 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48277 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48055 — Critical (CVSS 10.0): Streambert is a cross-platform Electron Desktop App to stream and download any video media. In versions 2.4.0 and…
CVE-2026-34910 — Critical (CVSS 10.0): A malicious actor with access to the network could exploit an Improper Input Validation vulnerability found in UniFi OS…
CVE-2026-33587 — Critical (CVSS 10.0): Lack of user input sanitisation in Open Notebook v1.8.3 allows the application user to execute Python code (and…

Browse all CWE-20 (Improper Input Validation) vulnerabilities →