CVE-2023-38545

CRITICAL

libcurl 7.69.0-8.4.0 - Heap-Based Buffer Overflow in SOCKS5 Proxy Handshake

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 10 public exploits for CVE-2023-38545. PoCs published by d0rb, UTsweetyfish, imfht.

AI-analyzed exploit summary This repository contains a functional exploit for CVE-2023-38545, targeting a SOCKS proxy server vulnerability. The PoC crafts a malicious HTTP response with a reverse shell payload to achieve remote code execution.

Description

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.

Exploits (10)

nomisec WORKING POC 22 stars
by d0rb · poc
https://github.com/d0rb/CVE-2023-38545

This repository contains a functional exploit for CVE-2023-38545, targeting a SOCKS proxy server vulnerability. The PoC crafts a malicious HTTP response with a reverse shell payload to achieve remote code execution.

Classification
Working Poc 90%
Attack Type
Rce
Complexity
Trivial
Reliability
Reliable
Target: SOCKS proxy server (version unspecified)
No auth needed
Prerequisites: Network access to the target SOCKS server · Target server must be vulnerable to CVE-2023-38545
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec SUSPICIOUS 19 stars
by UTsweetyfish · poc
https://github.com/UTsweetyfish/CVE-2023-38545

The repository contains a generic curl client and a Python script that reads from a file, but lacks any exploit-specific code or technical details about CVE-2023-38545. The README or additional context is missing, making it unclear how this relates to the vulnerability.

Classification
Suspicious 80%
Attack Type
Other
Complexity
Trivial
Reliability
Theoretical
Target: unknown
No auth needed
Prerequisites: unknown
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC 8 stars
by imfht · poc
https://github.com/imfht/CVE-2023-38545

This repository contains a functional proof-of-concept exploit for CVE-2023-38545, a heap-based buffer overflow vulnerability in curl 7.74.0. The exploit involves sending a crafted request with a large input to trigger the vulnerability, demonstrated via a Python script and a modified curl build.

Classification
Working Poc 90%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: curl 7.74.0
No auth needed
Prerequisites: curl 7.74.0 compiled with OpenSSL · Python 3 for running the socks.py script
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC 6 stars
by fatmo666 · poc
https://github.com/fatmo666/CVE-2023-38545-libcurl-SOCKS5-heap-buffer-overflow

This repository contains a functional PoC for CVE-2023-38545, a heap buffer overflow in libcurl's SOCKS5 proxy handling. The exploit triggers the vulnerability by sending a crafted 301 redirect with an excessively long hostname through a SOCKS5 proxy.

Classification
Working Poc 90%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: libcurl (versions affected by CVE-2023-38545)
No auth needed
Prerequisites: A vulnerable version of libcurl · A SOCKS5 proxy server · A web server to serve the malicious 301 redirect
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC 4 stars
by vanigori · poc
https://github.com/vanigori/CVE-2023-38545-sample

This repository contains a functional exploit for CVE-2023-38545, a heap-based buffer overflow in cURL. The exploit uses a malicious redirect server and a SOCKS5 proxy to trigger a segmentation fault in cURL when processing an overly long 'Location' header.

Classification
Working Poc 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: cURL 7.81.0
No auth needed
Prerequisites: Docker environment · Network access to the target
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC 3 stars
by bcdannyboy · poc
https://github.com/bcdannyboy/CVE-2023-38545

This repository contains a functional PoC for CVE-2023-38545, a heap buffer overflow vulnerability in curl versions 7.69.0 to 8.3.1. The exploit uses a SOCKS5 proxy and an HTTP server to trigger the vulnerability via crafted HTTP redirects with oversized payloads.

Classification
Working Poc 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: curl 7.69.0 to 8.3.1
No auth needed
Prerequisites: curl installed · network access to target · ability to run a local HTTP server and SOCKS5 proxy
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC 2 stars
by dbrugman · poc
https://github.com/dbrugman/CVE-2023-38545-POC

This repository contains a functional proof-of-concept exploit for CVE-2023-38545, a heap buffer overflow in the curl command-line tool when using SOCKS5 proxy with a rate limit. The PoC demonstrates the vulnerability by triggering a buffer overflow via a crafted HTTP response.

Classification
Working Poc 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Racy
Target: curl (command-line tool)
No auth needed
Prerequisites: Local SSH server for SOCKS5 proxy · Netcat (nc) installed
devstral-2 · analyzed Feb 18, 2026 Full analysis →
gitlab WORKING POC
by khadijaoussakel · poc
https://gitlab.com/khadijaoussakel/cve-2023-38545

This repository provides a functional proof-of-concept for CVE-2023-38545, a buffer overflow vulnerability in curl versions 7.69.0 to 8.3.0. It uses Docker containers to simulate a malicious HTTP server, a SOCKS5 proxy, and a vulnerable curl client to trigger a segmentation fault via a crafted hostname.

Classification
Working Poc 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: curl (7.69.0 to 8.3.0)
No auth needed
Prerequisites: Docker environment · curl version 7.69.0 to 8.3.0 · SOCKS5 proxy setup · malicious HTTP server with crafted response
devstral-2 · analyzed Feb 23, 2026 Full analysis →
nomisec WORKING POC
by nphuang · poc
https://github.com/nphuang/NS-Project-2024-Spring

This repository contains a functional exploit PoC for CVE-2023-38545, demonstrating a heap-based buffer overflow in cURL via a malicious SOCKS5 proxy. The exploit uses a crafted SOCKS5 proxy to trigger the vulnerability when cURL processes an overly long hostname.

Classification
Working Poc 90%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: cURL 7.74.0
No auth needed
Prerequisites: Docker environment · cURL compiled with OpenSSL support
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC
by Yang-Shun-Yu · poc
https://github.com/Yang-Shun-Yu/CVE-2023-38545

This repository contains a functional PoC for CVE-2023-38545, a heap buffer overflow vulnerability in curl versions 7.69.0 to 8.3.1. The exploit uses a SOCKS5 proxy and an HTTP server to trigger the vulnerability via crafted HTTP redirects with oversized payloads.

Classification
Working Poc 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: curl 7.69.0 to 8.3.1
No auth needed
Prerequisites: curl installed on target system · network access to SOCKS5 proxy and HTTP server
devstral-2 · analyzed Feb 18, 2026 Full analysis →

References (21)

Core 21
Core References
Patch, Third Party Advisory
https://curl.se/docs/CVE-2023-38545.html
Mailing List, Third Party Advisory
http://seclists.org/fulldisclosure/2024/Jan/34
Mailing List, Third Party Advisory
http://seclists.org/fulldisclosure/2024/Jan/37
Mailing List, Third Party Advisory
http://seclists.org/fulldisclosure/2024/Jan/38

Scores

CVSS v3 9.8
EPSS 0.7848
EPSS Percentile 99.5%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA SSVC

Vulnrichment
Exploitation poc
Automatable no
Technical Impact total

Details

CWE
CWE-787
Status published
Products (15)
curl/curl 7.69.0
curl/curl 8.4.0
fedoraproject/fedora 37
haxx/libcurl 7.69.0 - 8.4.0
microsoft/windows_10_1809 < 10.0.17763.5122
microsoft/windows_10_21h2 < 10.0.19044.3693
microsoft/windows_10_22h2 < 10.0.19045.3693
microsoft/windows_11_21h2 < 10.0.22000.2600
microsoft/windows_11_22h2 < 10.0.22621.2715
microsoft/windows_11_23h2 < 10.0.22631.2715
... and 5 more
Published Oct 18, 2023
Tracked Since Feb 18, 2026