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GHSA-84hm-wfh8-c5pg

MediumCVSS 6.6 / 10
Published May 5, 2026·Last modified May 5, 2026
Affected Components(0)

No affected components available

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

Risk Scores
Base Score
6.6

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.

Threat Intelligence
6.6

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.48%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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