Vulnerability-Lookup

FKIE_CVE-2026-19879

Vulnerability from fkie_nvd - Published: 2026-08-14 15:17 - Updated: 2026-08-14 19:07

Severity

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Summary

A flaw was found in Undertow, an HTTP server, within its HTTP response header writing path. The `writeString()` method performs a silent narrowing cast from 16-bit Unicode characters to 8-bit bytes when writing HTTP response header values. A remote attacker can exploit this by supplying specific Unicode characters in user-controlled input that an application places into response headers. This can lead to the truncation of these characters into ASCII control characters or special symbols, potentially resulting in limited integrity impact or information disclosure if the application does not properly sanitize user input.

References

	URL	Tags
	secalert@redhat.com	https://access.redhat.com/security/cve/CVE-2026-19879
	secalert@redhat.com	https://bugzilla.redhat.com/show_bug.cgi?id=2516038

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
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          "vendor": "Red Hat"
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          "product": "Red Hat Single Sign-On 7",
          "vendor": "Red Hat"
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      "value": "A flaw was found in Undertow, an HTTP server, within its HTTP response header writing path. The `writeString()` method performs a silent narrowing cast from 16-bit Unicode characters to 8-bit bytes when writing HTTP response header values. A remote attacker can exploit this by supplying specific Unicode characters in user-controlled input that an application places into response headers. This can lead to the truncation of these characters into ASCII control characters or special symbols, potentially resulting in limited integrity impact or information disclosure if the application does not properly sanitize user input."
    }
  ],
  "id": "CVE-2026-19879",
  "lastModified": "2026-08-14T19:07:46.080",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.3,
          "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:N",
          "version": "3.1"
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        "impactScore": 1.4,
        "source": "secalert@redhat.com",
        "type": "Secondary"
      }
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        "ssvcData": {
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          "options": [
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            {
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            {
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          "timestamp": "2026-08-14T17:41:34.677014Z",
          "version": "2.0.3"
        }
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  "references": [
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      "source": "secalert@redhat.com",
      "url": "https://access.redhat.com/security/cve/CVE-2026-19879"
    },
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      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2516038"
    }
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  "sourceIdentifier": "secalert@redhat.com",
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
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          "lang": "en",
          "value": "CWE-681"
        }
      ],
      "source": "secalert@redhat.com",
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    }
  ]
}

CVE-2026-19879 (GCVE-0-2026-19879)

Vulnerability from cvelistv5 – Published: 2026-08-14 14:51 – Updated: 2026-08-14 18:06

Title

Io.undertow/undertow: undertow: http response header integrity issue due to character truncation

Summary

Severity

5.3 (Medium)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-14 17:41 UTC

CWE

CWE-681 - Incorrect Conversion between Numeric Types

Assigner

redhat

References

2 references

URL	Tags
https://access.redhat.com/security/cve/CVE-2026-19879	vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2516038	issue-trackingx_refsource_REDHAT

Impacted products

8 products

Vendor	Product	Version
Red Hat	Red Hat build of Apache Camel for Spring Boot 4	cpe:/a:redhat:camel_spring_boot:4
Red Hat	Red Hat Enterprise Linux 10	cpe:/o:redhat:enterprise_linux:10
Red Hat	Red Hat Enterprise Linux 8	cpe:/o:redhat:enterprise_linux:8
Red Hat	Red Hat Enterprise Linux 9	cpe:/o:redhat:enterprise_linux:9
Red Hat	Red Hat JBoss Enterprise Application Platform 7	cpe:/a:redhat:jboss_enterprise_application_platform:7
Red Hat	Red Hat JBoss Enterprise Application Platform 8	cpe:/a:redhat:jboss_enterprise_application_platform:8
Red Hat	Red Hat JBoss Enterprise Application Platform Expansion Pack	cpe:/a:redhat:jbosseapxp
Red Hat	Red Hat Single Sign-On 7	cpe:/a:redhat:red_hat_single_sign_on:7

Date Public

2026-08-14 14:35

Show details on NVD website

JSON

To clipboard

{
  "containers": {
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        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-19879",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-14T17:41:34.677014Z",
                "version": "2.0.3"
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              "type": "ssvc"
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        "providerMetadata": {
          "dateUpdated": "2026-08-14T18:06:23.158Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
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        "title": "CISA ADP Vulnrichment"
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          "vendor": "Red Hat"
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          "vendor": "Red Hat"
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      "datePublic": "2026-08-14T14:35:09.145Z",
      "descriptions": [
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          "lang": "en",
          "value": "A flaw was found in Undertow, an HTTP server, within its HTTP response header writing path. The `writeString()` method performs a silent narrowing cast from 16-bit Unicode characters to 8-bit bytes when writing HTTP response header values. A remote attacker can exploit this by supplying specific Unicode characters in user-controlled input that an application places into response headers. This can lead to the truncation of these characters into ASCII control characters or special symbols, potentially resulting in limited integrity impact or information disclosure if the application does not properly sanitize user input."
        }
      ],
      "metrics": [
        {
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            "content": {
              "namespace": "https://access.redhat.com/security/updates/classification/",
              "value": "Moderate"
            },
            "type": "Red Hat severity rating"
          }
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "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:N",
            "version": "3.1"
          },
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            {
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              "description": "Incorrect Conversion between Numeric Types",
              "lang": "en",
              "type": "CWE"
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        "orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
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            "x_refsource_REDHAT"
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          "url": "https://access.redhat.com/security/cve/CVE-2026-19879"
        },
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          "name": "RHBZ#2516038",
          "tags": [
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            "x_refsource_REDHAT"
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          "time": "2026-08-14T14:14:58.978Z",
          "value": "Reported to Red Hat."
        },
        {
          "lang": "en",
          "time": "2026-08-14T14:35:09.145Z",
          "value": "Made public."
        }
      ],
      "title": "Io.undertow/undertow: undertow: http response header integrity issue due to character truncation",
      "workarounds": [
        {
          "lang": "en",
          "value": "Applications utilizing Undertow should implement robust input validation and sanitization for all user-controlled data before it is placed into HTTP response headers. It is recommended to restrict header values to printable ASCII characters (0x20\u20130x7E) at the application level. Where available, use framework-provided header-safe encoding mechanisms to ensure proper handling of special characters."
        }
      ],
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      },
      "x_redhatCweChain": "CWE-681: Incorrect Conversion between Numeric Types"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
    "assignerShortName": "redhat",
    "cveId": "CVE-2026-19879",
    "datePublished": "2026-08-14T14:51:36.106Z",
    "dateReserved": "2026-08-14T14:26:12.605Z",
    "dateUpdated": "2026-08-14T18:06:23.158Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
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}

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.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

FKIE_CVE-2026-19879

CVE-2026-19879 (GCVE-0-2026-19879)

Tags

Sightings

Nomenclature