VulnerabilityPublished 23 Sep 2026

CVE-2026-78437: Apache Tomcat · Incomplete Cleanup

Affects Apache TomcatSource CVE Database V5

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Not known to be exploited · CVSS 7.3 High · fixed in 9.0.122 : patch Apache Tomcat soon.

Data as of 7 Nov 2026, 23:24 UTC

CVSS 3.1 base score

7.3High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.5% chance of exploitation in 30 days – higher than 43% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 9.0.122

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 7 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Apache Software FoundationApache Tomcat	Affected >=11.0.19 <=11.0.25 >=10.1.53 <=10.1.59 >=9.0.116 <=9.0.121	Fixed in–
Mavenorg.apache.tomcat/tomcat`pkg:maven/org.apache.tomcat/tomcat`Other threats	Affected >=11.0.19 <=11.0.25 >=10.1.53 <=10.1.59 >=9.0.116 <=9.0.121	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Users should upgrade affected Apache Tomcat versions to 9.0.122, 10.1.60, or 11.0.26, where the vulnerability has been fixed. No other mitigation is indicated or required according to the vendor advisory.

Description

CVE-2026-78437 is an incomplete cleanup vulnerability in Apache Tomcat that may cause one user's request to fail due to a malformed request from another user, depending on timing. It affects Apache Tomcat versions 9.0.116 through 9.0.121, 10.1.53 through 10.1.59, and 11.0.19 through 11.0.25. The issue is fixed in versions 9.0.122, 10.1.60, and 11.0.26.

Impact

Successful exploitation can cause denial of service for a user request by causing it to fail due to incomplete cleanup triggered by a malformed request from another user. The CVSS score of 7.3 (high severity) reflects the network attack vector, low attack complexity, no privileges or user interaction required, and impacts on confidentiality, integrity, and availability, though the impact is limited to causing request failures rather than full system compromise.

CWE-459Incomplete Cleanup (opens in a new tab)
Base weakness
The product does not properly "clean up" and remove temporary or supporting resources after they have been used.
Architecture and Design · Implementation
Temporary files and other supporting resources should be deleted/released immediately after they are no longer needed.
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 17 Oct 2026, 23:39 UTC

WeaknessesCWE-459

Technical details

References

Community reviews

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