CVE-2026-91920 (GCVE-0-2026-91920)

Vulnerability from cvelistv5 – Published: 2026-10-30 01:16 – Updated: 2026-10-30 01:16
VLAI
Title
Undertow: undertow: chunkreader message length permits chunk-size overflow
Summary
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.
Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Assigner
redhat CNA under the redhat root
CNA scorecard B 82/100 over 1082 records in the last 180 days details
References
URL Tags
https://access.redhat.com/security/cve/CVE-2026-91920 vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2528758 issue-trackingx_refsource_REDHAT
Impacted products
Date Public
2026-10-29 12:11
Credits
Red Hat would like to thank Arpit Jain for reporting this issue.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "cpes": [
            "cpe:/a:redhat:camel_spring_boot:4"
          ],
          "defaultStatus": "affected",
          "packageName": "undertow-servlet",
          "product": "Red Hat build of Apache Camel for Spring Boot 4",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:8"
          ],
          "defaultStatus": "unknown",
          "packageName": "pki-core:10.6/resteasy",
          "product": "Red Hat Enterprise Linux 8",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:8"
          ],
          "defaultStatus": "unknown",
          "packageName": "pki-deps:10.6/resteasy",
          "product": "Red Hat Enterprise Linux 8",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:9"
          ],
          "defaultStatus": "unknown",
          "packageName": "resteasy",
          "product": "Red Hat Enterprise Linux 9",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "cpes": [
            "cpe:/a:redhat:jboss_fuse:7"
          ],
          "defaultStatus": "affected",
          "packageName": "undertow-servlet",
          "product": "Red Hat Fuse 7",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
          "cpes": [
            "cpe:/a:redhat:jboss_enterprise_application_platform:7"
          ],
          "defaultStatus": "affected",
          "packageName": "jboss-eap-7/eap74-els-openjdk11-openshift-rhel8",
          "product": "Red Hat JBoss Enterprise Application Platform 7",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
          "cpes": [
            "cpe:/a:redhat:jboss_enterprise_application_platform:7"
          ],
          "defaultStatus": "affected",
          "packageName": "jboss-eap-7/eap74-els-openjdk17-openshift-rhel8",
          "product": "Red Hat JBoss Enterprise Application Platform 7",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
          "cpes": [
            "cpe:/a:redhat:jboss_enterprise_application_platform:7"
          ],
          "defaultStatus": "affected",
          "packageName": "jboss-eap-7/eap74-els-openjdk8-openshift-rhel8",
          "product": "Red Hat JBoss Enterprise Application Platform 7",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
          "cpes": [
            "cpe:/a:redhat:jboss_enterprise_application_platform:7"
          ],
          "defaultStatus": "affected",
          "packageName": "undertow-servlet",
          "product": "Red Hat JBoss Enterprise Application Platform 7",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
          "cpes": [
            "cpe:/a:redhat:jboss_enterprise_application_platform:8"
          ],
          "defaultStatus": "affected",
          "packageName": "undertow-servlet",
          "product": "Red Hat JBoss Enterprise Application Platform 8",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
          "cpes": [
            "cpe:/a:redhat:jbosseapxp"
          ],
          "defaultStatus": "unaffected",
          "packageName": "undertow-servlet",
          "product": "Red Hat JBoss Enterprise Application Platform Expansion Pack",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "cpes": [
            "cpe:/a:redhat:red_hat_single_sign_on:7"
          ],
          "defaultStatus": "affected",
          "packageName": "undertow-servlet",
          "product": "Red Hat Single Sign-On 7",
          "vendor": "Red Hat"
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Red Hat would like to thank Arpit Jain for reporting this issue."
        }
      ],
      "datePublic": "2026-10-29T12:11:57.588Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
        {
          "other": {
            "content": {
              "namespace": "https://access.redhat.com/security/updates/classification/",
              "value": "Moderate"
            },
            "type": "Red Hat severity rating"
          }
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-444",
              "description": "Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-30T01:16:53.416Z",
        "orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
        "shortName": "redhat"
      },
      "references": [
        {
          "tags": [
            "vdb-entry",
            "x_refsource_REDHAT"
          ],
          "url": "https://access.redhat.com/security/cve/CVE-2026-91920"
        },
        {
          "name": "RHBZ#2528758",
          "tags": [
            "issue-tracking",
            "x_refsource_REDHAT"
          ],
          "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2528758"
        }
      ],
      "timeline": [
        {
          "lang": "en",
          "time": "2026-09-04T17:07:17.250Z",
          "value": "Reported to Red Hat."
        },
        {
          "lang": "en",
          "time": "2026-10-29T12:11:57.588Z",
          "value": "Made public."
        }
      ],
      "title": "Undertow: undertow: chunkreader message length permits chunk-size overflow",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      },
      "x_redhatCweChain": "CWE-444: Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
    "assignerShortName": "redhat",
    "cveId": "CVE-2026-91920",
    "datePublished": "2026-10-30T01:16:53.416Z",
    "dateReserved": "2026-09-15T10:20:33.140Z",
    "dateUpdated": "2026-10-30T01:16:53.416Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-91920",
      "date": "2026-10-30",
      "epss": "0.00235",
      "percentile": "0.14545"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
                "cpes": [
                  "cpe:/a:redhat:camel_spring_boot:4"
                ],
                "defaultStatus": "affected",
                "packageName": "undertow-servlet",
                "product": "Red Hat build of Apache Camel for Spring Boot 4",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
                "cpes": [
                  "cpe:/o:redhat:enterprise_linux:8"
                ],
                "defaultStatus": "unknown",
                "packageName": "pki-core:10.6/resteasy",
                "product": "Red Hat Enterprise Linux 8",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
                "cpes": [
                  "cpe:/o:redhat:enterprise_linux:8"
                ],
                "defaultStatus": "unknown",
                "packageName": "pki-deps:10.6/resteasy",
                "product": "Red Hat Enterprise Linux 8",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
                "cpes": [
                  "cpe:/o:redhat:enterprise_linux:9"
                ],
                "defaultStatus": "unknown",
                "packageName": "resteasy",
                "product": "Red Hat Enterprise Linux 9",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
                "cpes": [
                  "cpe:/a:redhat:jboss_fuse:7"
                ],
                "defaultStatus": "affected",
                "packageName": "undertow-servlet",
                "product": "Red Hat Fuse 7",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
                "cpes": [
                  "cpe:/a:redhat:jboss_enterprise_application_platform:7"
                ],
                "defaultStatus": "affected",
                "packageName": "jboss-eap-7/eap74-els-openjdk11-openshift-rhel8",
                "product": "Red Hat JBoss Enterprise Application Platform 7",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
                "cpes": [
                  "cpe:/a:redhat:jboss_enterprise_application_platform:7"
                ],
                "defaultStatus": "affected",
                "packageName": "jboss-eap-7/eap74-els-openjdk17-openshift-rhel8",
                "product": "Red Hat JBoss Enterprise Application Platform 7",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
                "cpes": [
                  "cpe:/a:redhat:jboss_enterprise_application_platform:7"
                ],
                "defaultStatus": "affected",
                "packageName": "jboss-eap-7/eap74-els-openjdk8-openshift-rhel8",
                "product": "Red Hat JBoss Enterprise Application Platform 7",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
                "cpes": [
                  "cpe:/a:redhat:jboss_enterprise_application_platform:7"
                ],
                "defaultStatus": "affected",
                "packageName": "undertow-servlet",
                "product": "Red Hat JBoss Enterprise Application Platform 7",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
                "cpes": [
                  "cpe:/a:redhat:jboss_enterprise_application_platform:8"
                ],
                "defaultStatus": "affected",
                "packageName": "undertow-servlet",
                "product": "Red Hat JBoss Enterprise Application Platform 8",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
                "cpes": [
                  "cpe:/a:redhat:jbosseapxp"
                ],
                "defaultStatus": "unaffected",
                "packageName": "undertow-servlet",
                "product": "Red Hat JBoss Enterprise Application Platform Expansion Pack",
                "vendor": "Red Hat"
              },
              {
                "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
                "cpes": [
                  "cpe:/a:redhat:red_hat_single_sign_on:7"
                ],
                "defaultStatus": "affected",
                "packageName": "undertow-servlet",
                "product": "Red Hat Single Sign-On 7",
                "vendor": "Red Hat"
              }
            ],
            "source": "secalert@redhat.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "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."
          }
        ],
        "id": "CVE-2026-91920",
        "lastModified": "2026-10-30T02:17:10.267",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "LOW",
                "baseScore": 6.5,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "LOW",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 2.5,
              "source": "secalert@redhat.com",
              "type": "Primary"
            }
          ]
        },
        "published": "2026-10-30T02:17:10.140",
        "references": [
          {
            "source": "secalert@redhat.com",
            "url": "https://access.redhat.com/security/cve/CVE-2026-91920"
          },
          {
            "source": "secalert@redhat.com",
            "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2528758"
          }
        ],
        "sourceIdentifier": "secalert@redhat.com",
        "vulnStatus": "Awaiting Analysis",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-444"
              }
            ],
            "source": "secalert@redhat.com",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-10-30T06:15:25+00:00",
      "cve": "CVE-2026-91920",
      "id": "CVE-2026-91920",
      "initial_release_date": "2026-10-29T12:11:57.588000+00:00",
      "product_status:known_affected": "8",
      "product_status:known_not_affected": "1",
      "product_status:under_investigation": "11",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "undertow: undertow: ChunkReader message length permits chunk-size overflow",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-91920.json",
      "version": "3"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.