CVE-2026-59083VulnerabilityPublished 14 Jul 2026Updated 4 Nov 2026

Tomcat6: Improper Handling of URL Encoding (Hex Encoding) vulnerability in Apache Tomcat's rewrite valve allowed

Affects tomcat6Source GCVE Database

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Authoritative record:CVE-2026-59083· Critical 9.1

Not known to be exploited · CVSS 9.1 Critical · fixed in 11.0.24 : patch tomcat6 as a priority.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 3.1 base score

9.1Critical

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 44% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 11.0.24

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

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

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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 14 Jul 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 4 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
Ubuntu 26.10tomcat10`pkg:deb/ubuntu/tomcat10?arch=source&distro=stonking`Other threats	Affected 10.1.40-1ubuntu1 – 10.1.57~us1-0ubuntu1 7 affected builds	Fixed in–
Ubuntu 26.10tomcat11`pkg:deb/ubuntu/tomcat11?arch=source&distro=stonking`Other threats	Affected 11.0.18-1 – 11.0.24-1ubuntu1 5 affected builds	Fixed in–
Ubuntu 26.10tomcat9`pkg:deb/ubuntu/tomcat9?arch=source&distro=stonking`Other threats	Affected =9.0.115-1 =9.0.115-1ubuntu1 =9.0.118-1	Fixed in–
Ubuntu 26.04 LTStomcat10`pkg:deb/ubuntu/tomcat10?arch=source&distro=resolute`Other threats	Affected =10.1.40-1ubuntu1 =10.1.40-1ubuntu1.26.04.1 =10.1.55-1ubuntu2~26.04.1	Fixed in–
Ubuntu 26.04 LTStomcat9`pkg:deb/ubuntu/tomcat9?arch=source&distro=resolute`Other threats	Affected 9.0.95-1ubuntu1 – 9.0.118-1~26.04.1 5 affected builds	Fixed in–
Ubuntu 26.04 LTStomcat11`pkg:deb/ubuntu/tomcat11?arch=source&distro=resolute`Other threats	Affected 11.0.6-1 – 11.0.22-2ubuntu2~26.04.1 6 affected builds	Fixed in–

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AI-suggested

Users should upgrade affected Apache Tomcat versions to 11.0.24, 10.1.57, or 9.0.120, which contain fixes for this vulnerability. No other mitigation or temporary workaround is indicated. Applying these official fixes fully addresses the issue.

Description

An improper handling of URL encoding (hex encoding) vulnerability in Apache Tomcat's rewrite valve allows security constraint bypass in certain configurations. This affects Apache Tomcat versions from 11.0.0-M1 through 11.0.23, 10.1.0-M1 through 10.1.56, 9.0.0-M1 through 9.0.119, and 8.5.0 through 8.5.100. The issue is fixed in versions 11.0.24, 10.1.57, and 9.0.120. The vulnerability has a critical severity with a CVSS score of 9.1.

Impact

Successful exploitation of this vulnerability allows an attacker to bypass security constraints configured via the rewrite valve in Apache Tomcat, potentially granting unauthorized access to protected resources. The impact includes high confidentiality and integrity compromise, but no impact on availability is indicated. The vulnerability does not require privileges or user interaction to exploit.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2026, 21:24 UTC

Technical details

References

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