CVE-2026-44214 json
eventsource-encoder: SSE event injection via unsanitized event and id fields
published 6mo ago modified 3mo ago also GHSA-m9g3-3g99-mhpx , EUVD-2026-31968
- cvss
- 5.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 20%
- public exploits
- 0
- none known
Summary
eventsource-encoder encodes events as well-formed EventSource/Server Sent Event (SSE) messages. Prior to 1.0.2, eventsource-encoder does not sanitize the event or id fields of an EventSourceMessage before serializing them. An attacker who controls either field can inject arbitrary Server-Sent Events line terminators (\n, \r, or \r\n) and thereby forge additional SSE fields or entire messages on the stream. This vulnerability is fixed in 1.0.2.
Patch / fix
- npm eventsource-encoder 1.0.2
- rexxars eventsource-encoder 1.0.2
Is CVE-2026-44214 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 5mo ago
Exploit prediction
0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-09).
Exploits and checks
- github.com https://github.com/rexxars/eventsource-encoder/security/advisories/GHSA-m9g3-3g99-mhpx referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N |
| NVD | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |
| GitHub | 3.1 | 5.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | eventsource-encoder | <1.0.2 |
1.0.2 |
Affected products
- rexxars eventsource-encoder
Classification
References
-
github.com
/rexxars/eventsource-encoder/security/advisories/GHSA-m9g3-3g99-mhpx
exploit, web, mitigation, vendor-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-44214
advisory
-
github.com
/rexxars/eventsource-encoder
package
-
html.spec.whatwg.org
/multipage/server-sent-events.html#parsing-an-event-stream
web
Sources
- CVE List CVE-2026-44214
- GitHub Advisory GHSA-m9g3-3g99-mhpx
- NVD CVE-2026-44214
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