CVE-2026-33128 | h3 has a Server-Sent Events Injection via Unsanitized Newlines in Event Stream Fields

Exp

H3 is a minimal H(TTP) framework. In versions prior to 1.15.6 and between 2.0.0 through 2.0.1-rc.14, createEventStream is vulnerable to Server-Sent Events (SSE) injection due to missing newline sanitization in formatEventStreamMessage() and formatEventStreamComment(). An attacker who controls any part of an SSE message field (id, event, data, or comment) can inject arbitrary SSE events to connected clients. This issue is fixed in versions 1.15.6 and 2.0.1-rc.15.

Published: 2026-03-20 Last update: 2026-03-20 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-33128 is rated Exploit Available (50/100): CVSS High severity, with low exploitation likelihood (EPSS 0.04%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

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

Public exploit references (Exploit-DB) for CVE-2026-33128

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-33128

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 2026-03-20 — 0.04% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-33128

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/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:L)
Some sensitive info could get out, but not a total data dump.
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 4.7 [email protected]
10.0 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H 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: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:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 6.0 [email protected]

Weakness enumeration for CVE-2026-33128

GitHub Security Advisory for CVE-2026-33128

GHSA-22cc-p3c6-wpvm · Severity: high · Ecosystem: npm — h3 has a Server-Sent Events Injection via Unsanitized Newlines in Event Stream Fields

Affected software / configurations for CVE-2026-33128

Vendor Product Version Raw CPE
h3 h3 < 1.15.6 cpe:2.3:a:h3:h3:*:*:*:*:*:node.js:*:*
h3 h3 2.0.0 cpe:2.3:a:h3:h3:2.0.0:*:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc10:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc11:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc12:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc13:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc14:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc2:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc3:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc4:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc5:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc6:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc7:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc8:*:*:*:node.js:*:*
h3 h3 2.0.1 cpe:2.3:a:h3:h3:2.0.1:rc9:*:*:*:node.js:*:*

References for CVE-2026-33128

cvelogic Threat Intelligence