Red Hat Undertow ChunkReader input validation

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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6.5$5k-$25k1.14-

Summaryinfo

A vulnerability was found in Red Hat Undertow. It has been classified as critical. Affected by this issue is some unknown functionality of the component ChunkReader. The manipulation leads to input validation. This vulnerability is referenced as CVE-2026-91920. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Red Hat Undertow (unknown version). This issue affects an unknown code block of the component ChunkReader. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is integrity, and availability. The summary by CVE is:

A flaw was found in the ChunkReader component of the Undertow web server, which is used to handle chunked transfer encoding in HTTP requests. The issue occurs because a security check for the chunk size is performed before the value is shifted, allowing a specifically crafted 15-digit chunk size to bypass the limit and overflow into internal state flags. This can cause the server to terminate a request body prematurely and interpret the remaining data as a separate, smuggled request.

The advisory is shared at access.redhat.com. The identification of this vulnerability is CVE-2026-91920 since 09/15/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 10/30/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

Name

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.5
VulDB Meta Temp Score: 6.5

VulDB Base Score: 6.5
VulDB Temp Score: 6.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 6.5
CNA Vector (redhat): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Input validation
CWE: CWE-20
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

09/15/2026 CVE reserved
10/30/2026 +45 days Advisory disclosed
10/30/2026 +0 days VulDB entry created
10/30/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: redhat.com

Advisory: access.redhat.com
Status: Not defined

CNA: redhat
CVE: CVE-2026-91920 (🔒)

GCVE (CVE): GCVE-0-2026-91920
GCVE (VulDB): GCVE-100-428825

Entryinfo

Created: 10/30/2026 02:39
Changes: 10/30/2026 02:39 (60)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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