CVE-2023-26103
CVSS v3
7.5
HIGH
EPSS Score
1.2 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
—
SSVC status
Description
Versions of the package deno before 1.31.0 are vulnerable to Regular Expression Denial of Service (ReDoS) due to the upgradeWebSocket function, which contains regexes in the form of /s*,s*/, used for splitting the Connection/Upgrade header. A specially crafted Connection/Upgrade header can be used to significantly slow down a web socket server.
Technical details
- Published
- 2023-02-25
Frequently asked questions
What is CVE-2023-26103?
Versions of the package deno before 1.31.0 are vulnerable to Regular Expression Denial of Service (ReDoS) due to the upgradeWebSocket function, which contains regexes in the form of /s*,s*/, used for splitting the Connection/Upgrade header. A specially crafted Connection/Upgrade header can be used to significantly slow down a web socket server.
Is CVE-2023-26103 actively exploited?
Active exploitation of CVE-2023-26103 has not been confirmed. Its EPSS score was 1.2% on 2026-09-25, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2023-26103?
CVE-2023-26103 has a CVSS v3 base score of 7.5 (HIGH severity).
Is CVE-2023-26103 affecting your environment?
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