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Vulnerability record · public intelligence
CVE-2020-7663
UNKNOWN

Regular Expression Denial of Service in websocket-extensions (RubyGem)

Published Jun 2, 2020 · Updated Nov 3, 2026

Severity · CVSSUNKNOWN · Not scored
Known exploitationNot listed
EPSS / likelihood4.64%
QFinch risk scoreNot available

Original summary

Normalized public record · Updated Nov 3, 2026

Regular Expression Denial of Service in websocket-extensions (RubyGem)

Publisher and source text is retained separately from QFinch interpretation.

QFinch assessment

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:

Potential 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: 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.

Evidence: public source records

Affected products

Affected scope reported by the available public evidence
Affected package, product or rangeFix status
Consult the referenced vendor advisory for affected versions.Consult source advisory

Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.

Remediation

Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.

  1. Confirm the affected product and reachable code path exist in your environment.
  2. Apply the vendor-supported patch or mitigation from the primary advisory.
  3. Rescan the exact deployed revision and retain verification evidence.
Review primary references

Evidence coverage

FIRST-EPSSCVE-LIST-V5
SSVC priority
MEDIUM
Confidence
Not available
Aliases
None reported

Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.

Sources and record history

  1. Security advisory ↗
  2. Patch commit ↗
  3. blog.jcoglan.com ↗
  4. snyk.io ↗
  5. [debian-lts-announce] 20200819 [SECURITY] [DLA 2334-1] ruby-websocket-extensions security update ↗
  6. USN-4502-1 ↗

Record history

Published Jun 2, 2020 · Last refreshed Nov 3, 2026

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