sse-channel: SSE Injection via unsanitized event fields

CVE-2026-44217 → View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

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

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2026-05-05 22:17:02 UTC
Updated
2026-05-13 16:27:29 UTC
GitHub reviewed
2026-05-05 22:17:02 UTC
NVD published
2026-05-12

EPSS Score

Score Percentile
0.05% 14.61%

CVSS Scores

Base score Version Severity Vector
6.6 4.0 —
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network.
Attack complexity (AC:L)
Exploitation conditions are straightforward and stable.
Attack requirements (AT:N)
No additional preconditions are required beyond normal reachability.
Privileges required (PR:N)
No privileges are required.
User interaction (UI:N)
No user interaction is required.
Vulnerable system confidentiality impact (VC:N)
No confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:H)
High integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:N)
No availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:N)
No confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:N)
No integrity impact on subsequent systems.
Subsequent system availability impact (SA:N)
No availability impact on subsequent systems.
Exploit maturity (threat) (E:U)
Unreported: no public PoC, no reported exploitation, and no known simplification tools.

Identifiers

Type Value
GHSA GHSA-84hm-wfh8-c5pg ↗
CVE CVE-2026-44217 ↗

CWEs

CWE id Name
CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')

Credits

  • SnailSploit (reporter)

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
npm sse-channel <= 4.0.0 4.0.1 —

References

cvelogic Threat Intelligence