CVE-2023-26103

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

1.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2023-02-25 05:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 05:42 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.2% in the next 30 days (EPSS).
• Severity: 5.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2023-02-25 05:15 UTC

Last modified

2026-06-17 05:42 UTC

Exploit probability

1.2% · EPSS, next 30 days

Weakness

CWE-1333

Record status

Modified

Affected

• Deno < 1.31.0

Attack profile CVSS 3.1 · 5.3

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2023-26103.md and follow it. Check whether this project is affected by CVE-2023-26103. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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