CVE-2026-44214: eventsource-encode — Exploit & Fix

Description

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.

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CVSS v3.1 Score

5.8

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0026

Probability of exploitation

0.17%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-93 CWE-93

CWE-113 CWE-113

Affected Products

Vendor	Product	Versions
rexxars	eventsource-encoder	< 1.0.2

References

Advisories & Patches

https://github.com/rexxars/eventsource-encoder/security/advisories/GHSA-m9g3-3g99-mhpx https://github.com/rexxars/eventsource-encoder/security/advisories/GHSA-m9g3-3g99-mhpx

Exploits

https://github.com/rexxars/eventsource-encoder/security/advisories/GHSA-m9g3-3g99-mhpx https://github.com/rexxars/eventsource-encoder/security/advisories/GHSA-m9g3-3g99-mhpx

Frequently Asked Questions

What is CVE-2026-44214? +

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. It has a CVSS v3.1 base score of 5.8 (MEDIUM).

How severe is CVE-2026-44214? +

CVE-2026-44214 has a CVSS v3.1 score of 5.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0026, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-44214? +

CVE-2026-44214 affects products from rexxars, specifically: eventsource-encoder. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-44214? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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