CVE-2023-38545

What it is

This flaw makes curl overflow a heap based buffer in the SOCKS5 proxy handshake. When curl is asked to pass along the host name to the SOCKS5 proxy to allow that to resolve the address instead of it getting done by curl itself, the maximum length that host name can be is 255 bytes. If the host name is detected to be longer, curl switches to local name resolving and instead passes on the resolved address only. Due to this bug, the local variable that means "let the host resolve the name" could get the wrong value during a slow SOCKS5 handshake, and contrary to the intention, copy the too long host name to the target buffer instead of copying just the resolved address there. The target buffer being a heap based buffer, and the host name coming from the URL that curl has been told to operate with.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

78.3% chance of exploitation in the next 30 days (EPSS). Higher than most.

Fix

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

Timeline

1. 2023-07-20 01:00 UTC ReservedThe CVE id was reserved by its CNA
2. 2023-10-18 04:15 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-06-17 06:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 78.3% in the next 30 days (EPSS).
• Severity: 9.8 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.
• It meets the bar for Drop everything: critical, and exploited or very likely to be.

Details

Published

2023-10-18 04:15 UTC

Last modified

2026-06-17 06:10 UTC

Exploit probability

78.3% · EPSS, next 30 days

Weakness

CWE-787 · Out-of-bounds write

Record status

Modified

Affected

• Haxx Libcurl < 8.4.0
• Fedoraproject Fedora 37
• Netapp Active Iq Unified Manager
• Netapp Oncommand Insight
• Netapp Oncommand Workflow Automation
• Microsoft Windows 10 1809 < 10.0.17763.5122
• Microsoft Windows 10 21h2 < 10.0.19044.3693
• Microsoft Windows 10 22h2 < 10.0.19045.3693

Attack profile CVSS 3.1 · 9.8

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

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-2023-38545.md and follow it. Check whether this project is affected by CVE-2023-38545. 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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