CVE-2026-19879Network attack vector

Response-header corruption via Unicode character truncation

Published Aug 14, 2026 · Updated Aug 14, 2026

Incorrect numeric conversion in Undertow in affected Red Hat products allows remote attackers to corrupt HTTP response headers. The response-header writeString() path silently narrows each 16-bit Unicode character to an 8-bit byte, turning selected values into ASCII controls or special symbols. Exploitation requires an application to place unsanitized attacker-controlled Unicode into a response header; Undertow blocks response splitting, bounding the reported impact to limited header integrity effects.

CVSS severity5.3
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect numeric conversion in Undertow in affected Red Hat products allows remote attackers to corrupt HTTP response headers. The response-header writeString() path silently narrows each 16-bit Unicode character to an 8-bit byte, turning selected values into ASCII controls or special symbols. Exploitation requires an application to place unsanitized attacker-controlled Unicode into a response header; Undertow blocks response splitting, bounding the reported impact to limited header integrity effects.

The record

CVE
CVE-2026-19879
Published
Aug 14, 2026
Updated
Aug 14, 2026
Vendor
389 Directory Server
Product
Red Hat JBoss Enterprise Application Platform Expansion Pack
Classifications
CWE-681, T1565
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

389 Directory Server · Red Hat JBoss Enterprise Application Platform Expansion PackAffected versions are unavailable in this record.
389 Directory Server · Red Hat build of Apache Camel for Spring BootAffected versions are unavailable in this record.
389 Directory Server · Red Hat Single Sign-On 7Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 10Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9Affected versions are unavailable in this record.
389 Directory Server · Red Hat JBoss Enterprise Application PlatformAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8Affected versions are unavailable in this record.

Published CVSS scores

5.3Red HatCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-681Incorrect Conversion between Numeric Types
T1565Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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