What’s Vulnerable › Vulnerabilities

CVE-2023-26103

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2023-02-25 · updated 2026-06-17
• Weakness: CWE-1333

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.

Affected products

• denoland deno: before 1.31.0 — fixed in 1.31.0

How to fix

Upgrade to a fixed version: denoland deno 1.31.0. Check the vendor advisory for mitigations.

References

• https://github.com/denoland/deno/blob/2b247be517d789a37e532849e2e40b724af0918f/ext/http/01_http.js%23L395-L409
• https://github.com/denoland/deno/commit/cf06a7c7e672880e1b38598fe445e2c50b4a9d06
• https://github.com/denoland/deno/pull/17722
• https://github.com/denoland/deno/releases/tag/v1.31.0
• https://security.snyk.io/vuln/SNYK-RUST-DENO-3315970
• https://github.com/denoland/deno/blob/2b247be517d789a37e532849e2e40b724af0918f/ext/http/01_http.js%23L395-L409
• https://github.com/denoland/deno/commit/cf06a7c7e672880e1b38598fe445e2c50b4a9d06
• https://github.com/denoland/deno/pull/17722
• https://github.com/denoland/deno/releases/tag/v1.31.0
• https://security.snyk.io/vuln/SNYK-RUST-DENO-3315970

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