CVE-2026-28367 | Undertow: undertow: request smuggling via `\r\r\r` as a header block terminator

A flaw was found in Undertow. A remote attacker can exploit this vulnerability by sending `\r\r\r` as a header block terminator. This can be used for request smuggling with certain proxy servers, such as older versions of Apache Traffic Server and Google Cloud Classic Application Load Balancer, potentially leading to unauthorized access or manipulation of web requests.

Published: 2026-03-27 Last update: 2026-04-10 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-28367 is rated Low Risk (38.5/100): CVSS High severity, with low exploitation likelihood (EPSS 0.04%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-28367

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-28 — 0.04% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-28367

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.7 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 5.8 [email protected]
9.1 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 5.2 [email protected]

Weakness enumeration for CVE-2026-28367

GitHub Security Advisory for CVE-2026-28367

GHSA-3gv6-g396-9v4r · Severity: high · Ecosystem: maven — Undertow is Vulnerable to HTTP Request/Response Smuggling

OS Trackers for CVE-2026-28367

vendor priority summary link
debian not yet assigned CVE-2026-28367 not yet assigned priority: Debian including 1 source packages (undertow), 2 status rows across 2 suites (forky, sid): open 2. https://security-tracker.debian.org/tracker/CVE-2026-28367
redhat high — https://access.redhat.com/security/cve/CVE-2026-28367
ubuntu medium CVE-2026-28367 medium priority: Ubuntu including 1 source packages (undertow), 7 status rows across 7 suites (bionic, focal, jammy, noble, questing, upstream, xenial): needs-triage 7. https://ubuntu.com/security/CVE-2026-28367

Affected software / configurations for CVE-2026-28367

Vendor Product Version Raw CPE
redhat build_of_apache_camel_-_hawtio 4.0 cpe:2.3:a:redhat:build_of_apache_camel_-_hawtio:4.0:*:*:*:*:*:*:*
redhat build_of_apache_camel_for_spring_boot 4.0 cpe:2.3:a:redhat:build_of_apache_camel_for_spring_boot:4.0:*:*:*:*:*:*:*
redhat data_grid 8.0 cpe:2.3:a:redhat:data_grid:8.0:*:*:*:*:*:*:*
redhat fuse 7.0.0 cpe:2.3:a:redhat:fuse:7.0.0:*:*:*:*:*:*:*
redhat jboss_enterprise_application_platform 7.0.0 cpe:2.3:a:redhat:jboss_enterprise_application_platform:7.0.0:*:*:*:*:*:*:*
redhat jboss_enterprise_application_platform 8.0.0 cpe:2.3:a:redhat:jboss_enterprise_application_platform:8.0.0:*:*:*:*:*:*:*
redhat jboss_enterprise_application_platform_expansion_pack — cpe:2.3:a:redhat:jboss_enterprise_application_platform_expansion_pack:-:*:*:*:*:*:*:*
redhat process_automation 7.0 cpe:2.3:a:redhat:process_automation:7.0:*:*:*:*:*:*:*
redhat single_sign-on 7.0 cpe:2.3:a:redhat:single_sign-on:7.0:*:*:*:*:*:*:*
redhat undertow — cpe:2.3:a:redhat:undertow:-:*:*:*:*:*:*:*

References for CVE-2026-28367

cvelogic Threat Intelligence