CVE-2023-26103

Name: CVE-2023-26103
Creator: NVD / NIST
Published: 2023-02-25T05:15:12.343+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.23%

Last modified Jun 17, 2026

CVE-2023-26103 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. . EPSS estimates a 1.23% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

1.23%

65.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Deno	Deno	< 1.31.0

References

https://github.com/denoland/deno/blob/2b247be517d789a37e532849e2e40b724af0918f/ext/http/01_http.js%23L395-L409Broken Link
https://github.com/denoland/deno/commit/cf06a7c7e672880e1b38598fe445e2c50b4a9d06Patch
https://github.com/denoland/deno/pull/17722Patch
https://github.com/denoland/deno/releases/tag/v1.31.0Release Notes
https://security.snyk.io/vuln/SNYK-RUST-DENO-3315970Exploit, Technical Description, Third Party Advisory
https://github.com/denoland/deno/blob/2b247be517d789a37e532849e2e40b724af0918f/ext/http/01_http.js%23L395-L409Broken Link
https://github.com/denoland/deno/commit/cf06a7c7e672880e1b38598fe445e2c50b4a9d06Patch
https://github.com/denoland/deno/pull/17722Patch
https://github.com/denoland/deno/releases/tag/v1.31.0Release Notes
https://security.snyk.io/vuln/SNYK-RUST-DENO-3315970Exploit, Technical Description, Third Party Advisory

Timeline

Published: Feb 25, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-26103?

How severe is CVE-2023-26103?

CVE-2023-26103 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.23% probability of exploitation in the next 30 days.

How do I fix CVE-2023-26103?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2023-26103?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST