# CVE-2026-44217: sse-channel — Fixed in 4.0.1

📦 npm

Not in CISA KEV

# CVE-2026-44217 — sse-channel

CVE-2026-44217 is a CWE-93 vulnerability in sse-channel. A fix is available for sse-channel — see the affected versions and patch details below.

sse-channel: SSE Injection via unsanitized event fields

Also known as[GHSA-84hm-wfh8-c5pg](/vulnerability/GHSA-84hm-wfh8-c5pg)

Published

May 12, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### No confirmed exploitation observed yet

-   CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
-   CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44217.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs41th percentile — riskier than 41% of all scored CVEsHighest risk

0.00%0.35%0.69%1.04%0.0%0.5%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

30other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

`sse-channel`npm

2Kdownloads / week

## Description

#### Impact

Implementations that allows user-provided values to be passed to `event`, `retry` or `id` fields would be susceptible to event spoofing, where an attacker could inject arbitrary messages into the stream.

-   **Event Spoofing:** Attacker can inject arbitrary SSE events into the stream
-   **Client-side Manipulation:** Injected events can trigger unintended behavior in frontend JavaScript EventSource listeners
-   **Data Integrity:** Consumers of the SSE stream cannot distinguish injected events from legitimate ones

#### Patches

Patch available in v4.0.1.

#### Workarounds

Do not allow user data to control `event`, `retry` or `id` fields, and if you must - sanitize the input before passing it to `sse-channel`, stripping any newlines.

#### Resources

[https://github.com/rexxars/sse-channel/issues/42](https://github.com/rexxars/sse-channel/issues/42)

## Affected Packages

1 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

📦npm

`sse-channel` 

all versions

4.0.1`npm install sse-channel@4.0.1`

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for sse-channel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Fix
    
    Update sse-channel to 4.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44217 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
    

## Frequently Asked Questions

\### Impact Implementations that allows user-provided values to be passed to \`event\`, \`retry\` or \`id\` fields would be susceptible to event spoofing, where an attacker could inject arbitrary messages into the stream. - \*\*Event Spoofing:\*\* Attacker can inject arbitrary SSE events into the stream - \*\*Client-side Manipulation:\*\* Injected events can trigger unintended behavior in frontend JavaScript EventSource listeners - \*\*Data Integrity:\*\* Consumers of the SSE stream cannot distinguish injected events from legitimate ones ### Patches Patch available in v4.0.1. ### Workarounds Do not allow use

O3 Security · Impact-Aware SCA

### Is CVE-2026-44217 in your dependencies?

Find it across npm, including transitive dependencies.

[Scan my dependencies](/book-demo) [How O3 SCA works](/impact-aware-sca)