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GHSA-g6wq-qcwm-j5g2

HighCVSS 8.2 / 10

Published Jun 5, 2020·Last modified Mar 13, 2026

Affected Components(0)

No affected components available

Description

Impact

The ReDoS flaw allows an attacker to exhaust the server's capacity to process incoming requests by sending a WebSocket handshake request containing a header of the following form:

Sec-WebSocket-Extensions: a; b="\c\c\c\c\c\c\c\c\c\c ...

That is, a header containing an unclosed string parameter value whose content is a repeating two-byte sequence of a backslash and some other character. The parser takes exponential time to reject this header as invalid, and this will block the processing of any other work on the same thread. Thus if you are running a single-threaded server, such a request can render your service completely unavailable.

Patches

Users should upgrade to version 0.1.5.

Workarounds

There are no known work-arounds other than disabling any public-facing WebSocket functionality you are operating.

References

https://blog.jcoglan.com/2020/06/02/redos-vulnerability-in-websocket-extensions/

Risk Scores

Base Score

8.2

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. The impact is confined to the system where the vulnerability exists. There is a low impact on the integrity of the data. There is a high impact on the availability of the system.

Threat Intelligence

7.5

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS

4.40%

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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High severity

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