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CVE-2023-38545 critical CVSS 9.8

Out-of-Bounds Write in Microsoft Haxx (CVE-2023-38545)

Summary

Out-of-bounds write in Microsoft Haxx (CVE-2023-38545). Successful exploitation can lead to full system takeover.

Original description

The description as published by the source.

This flaw makes curl overflow a heap based buffer in the SOCKS5 proxy
handshake.

When curl is asked to pass along the hostname to the SOCKS5 proxy to allow
that to resolve the address instead of it getting done by curl itself, the
maximum length that hostname can be is 255 bytes.

If the hostname is detected to be longer than 255 bytes, curl switches to
local name resolving and instead passes on the resolved address only to the
proxy. Due to a 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 hostname to the target buffer instead of
copying only the resolved address there.

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2023-38545 has been found in Microsoft Haxx.
Successful exploitation can lead to full system takeover. CVSS score: 9.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Microsoft Haxx CVE-2023-38545" on the vendor's site.

CVE-2023-38545 (Microsoft Haxx) — CWE-787 / CVSS v3 9.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Out-of-bounds write (CWE-787) exists in Microsoft Haxx.

📍 Affected scope

Check the vendor advisory for the affected versions of Microsoft Haxx.

🔥 Severity

Severity: Critical (CVSS 9.8/10). Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Haxx' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'Haxx' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で Haxx を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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