Summary
When using streamSSE() in Streaming Helper, the event, id, and retry fields were not validated for carriage return (\r) or newline (\n) characters.
Because the SSE protocol uses line breaks as field delimiters, this could allow injection of additional SSE fields within the same event frame if untrusted input was passed into these fields.
Details
The SSE helper builds event frames by joining lines with \n. While multi-line data: fields are handled according to the SSE specification, the event, id, and retry fields previously allowed raw values without rejecting embedded CR/LF characters.
Including CR/LF in these control fields could allow unintended additional fields (such as data:, id:, or retry:) to be injected into the event stream.
The issue has been fixed by rejecting CR/LF characters in these fields.
Impact
An attacker could manipulate the structure of SSE event frames if an application passed user-controlled input directly into event, id, or retry.
Depending on application behavior, this could result in injected SSE fields or altered event stream handling. Applications that render e.data in an unsafe manner (for example, using innerHTML) could potentially expose themselves to client-side script injection.
This issue affects applications that rely on the SSE helper to enforce protocol-level constraints.
References
TarPeg007 Reporter
Summary
When using
streamSSE()in Streaming Helper, theevent,id, andretryfields were not validated for carriage return (\r) or newline (\n) characters.Because the SSE protocol uses line breaks as field delimiters, this could allow injection of additional SSE fields within the same event frame if untrusted input was passed into these fields.
Details
The SSE helper builds event frames by joining lines with
\n. While multi-linedata:fields are handled according to the SSE specification, theevent,id, andretryfields previously allowed raw values without rejecting embedded CR/LF characters.Including CR/LF in these control fields could allow unintended additional fields (such as
data:,id:, orretry:) to be injected into the event stream.The issue has been fixed by rejecting CR/LF characters in these fields.
Impact
An attacker could manipulate the structure of SSE event frames if an application passed user-controlled input directly into
event,id, orretry.Depending on application behavior, this could result in injected SSE fields or altered event stream handling. Applications that render
e.datain an unsafe manner (for example, usinginnerHTML) could potentially expose themselves to client-side script injection.This issue affects applications that rely on the SSE helper to enforce protocol-level constraints.
References