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Vulnerabilities

Vulnerability · CVE-2009-0580

Apache Tomcat 4.1.0 through 4.1.39, 5.5.0 through 5.5.27, and 6.0.0 through 6.0.18, when FORM authentication is used, allows remote attackers to enumerate valid userna…

Published Jun 5, 2009 · catalog updated Jun 16, 2026 · the affected product

Last checked Nov 3, 2026. A connected source was read within the last 7 days.

Check this week

CVE-2009-0580 is not in CISA KEV. FIRST estimates a 94.44% chance of exploitation in the next 30 days. Check whether you run the affected product.

Gaps on this record

  • No plain product name is stored. The page cannot tell you which product to check.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Medium4.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
94.44%
Remediation
Advisory link
Affected products
cpe apache/tomcat

Apache Tomcat 4.1.0 through 4.1.39, 5.5.0 through 5.5.27, and 6.0.0 through 6.0.18, when FORM authentication is used, allows remote attackers to enumerate valid usernames via requests to /j_security_check with malformed URL encoding of passwords, related to improper error checking in the (1) MemoryRealm, (2) DataSourceRealm, and (3) JDBCRealm authentication realms, as demonstrated by a % (percent) value for the j_password parameter.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe apache/tomcat4.1.0
  • cpe apache/tomcat4.1.1
  • cpe apache/tomcat4.1.2
  • cpe apache/tomcat4.1.3
  • cpe apache/tomcat4.1.4

How to fix CVE-2009-0580

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2009-0580 is not in CISA KEV. FIRST estimates a 94.44% chance of exploitation in the next 30 days. Check whether you run the affected product.

Which versions are affected?

Compare what you have installed with 4.1.0, 4.1.1, 4.1.2, 4.1.3, 4.1.4. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-200: Exposure of Sensitive Information. EPSS 94.44%. There is no CISA KEV listing. A public exploit reference is linked in Sources. That is not the same as confirmed exploitation. Use the source links for the original advisory.

Technology hubs

Apache Tomcat security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Jun 5, 2009 · Monitored products — critical

    Detected

    Apache Tomcat 4.1.0 through 4.1.39, 5.5.0 through 5.5.27, and 6.0.0 through 6.0.18, when FORM authentication is used, allows remote attackers to enumerate valid usernames via requests to /j_security_check with malformed URL encoding of passwords, related to improper error checking in the (1) MemoryRealm, (2) DataSourceRealm, and (3) JDBCRealm authentication realms, as demonstrated by a % (percent)

  2. Jun 16, 2026 · Monitored products — critical

    Updated

    Apache Tomcat 4.1.0 through 4.1.39, 5.5.0 through 5.5.27, and 6.0.0 through 6.0.18, when FORM authentication is used, allows remote attackers to enumerate valid usernames via requests to /j_security_check with malformed URL encoding of passwords, related to improper error checking in the (1) MemoryRealm, (2) DataSourceRealm, and (3) JDBCRealm authentication realms, as demonstrated by a % (percent)

Sources

  • FIRST EPSSExploitation probabilityCVE-2009-0580

    30-day exploitation probability 94.44%

    first.org
  • Monitored products — criticalVendor advisoryCVE-2009-0580

    Apache Tomcat 4.1.0 through 4.1.39, 5.5.0 through 5.5.27, and 6.0.0 through 6.0.18, when FORM authentication is used, allows remote attackers to enumerate valid usernames via requests to /j_security_check with malformed URL encoding of passwords, related to improper error checking in the (1) MemoryRealm, (2) DataSourceRealm, and (3) JDBCRealm authentication realms, as demonstrated by a % (percent)

    nvd.nist.gov
  • Metasploit ModulesPublic exploit moduleauxiliary_scanner/http/tomcat_enum

    Public module reference (normal). Module source is not copied into this catalog.

    rapid7.com

References

Freshness

Last verified in this catalog Nov 3, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 3, 2026
  • Metasploit ModulesNov 3, 2026
  • Monitored products — criticalNov 3, 2026