Description
3proxy from 0.9.7 through 1.0.1, fixed in commit 206c923, contains an uninitialized stack memory disclosure vulnerability that allows unauthenticated attackers to leak stack bytes via the SOCKS4 reply path when the external-NAT option (-Ne) is configured. Attackers can send a client probe that fails the SOCKS version check to trigger a reply containing uninitialized bytes from the sin structure, exposing high bytes of a userspace pointer that weakens ASLR protections.
Published: 2026-10-14
Score: 6.3 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Information disclosure that weakens ASLR protections via stack memory leakage
Action: Apply patch
AI Analysis

Impact

This vulnerability allows an unauthenticated attacker to trigger a reply in the SOCKS4 protocol that contains uninitialized stack bytes when the external‑NAT option is enabled. By sending a client packet that fails the SOCKS version check, the server sends a reply that includes raw contents from the "sin" structure, leaking high bytes of a user‑space pointer. This exposure undermines ASLR and can aid further exploitation. The vulnerability is a classic uninitialized memory disclosure and is classified as CWE‑908.

Affected Systems

The issue affects the 3proxy proxy server, versions 0.9.7 through 1.0.1 inclusive. Operators using any of these releases should verify their version and the configuration of the external‑NAT option (-Ne).

Risk and Exploitability

The CVSS score of 6.3 indicates a moderate severity. The EPSS score of 0.00358 (<1%) indicates a low but non‑zero exploitation probability. The flaw is network‑based and does not require authentication, making it an attractive target for attackers. It is not listed in the CISA KEV catalog. Exploitation requires only a SOCKS4 client and the target must have the external‑NAT option enabled, which is a relatively permissive attack vector.

Generated by OpenCVE AI on October 15, 2026 at 18:55 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade 3proxy to a release that includes the fix from commit 206c923.
  • If an upgrade is not immediately possible, disable the external‑NAT option (-Ne) so the vulnerable reply path is never exercised.
  • Continuously monitor SOCKS4 traffic for abnormal or failed version checks and review logs for evidence of uninitialized memory leaks.

Generated by OpenCVE AI on October 15, 2026 at 18:55 UTC.

Tracking

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Advisories

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History

Tue, 27 Oct 2026 04:30:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:3proxy:3proxy:*:*:*:*:*:*:*:*

Fri, 23 Oct 2026 00:45:00 +0000

Type Values Removed Values Added
First Time appeared 3proxy
3proxy 3proxy
Vendors & Products 3proxy
3proxy 3proxy

Thu, 15 Oct 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 14 Oct 2026 16:00:00 +0000

Type Values Removed Values Added
Description 3proxy from 0.9.7 through 1.0.1, fixed in commit 206c923, contains an uninitialized stack memory disclosure vulnerability that allows unauthenticated attackers to leak stack bytes via the SOCKS4 reply path when the external-NAT option (-Ne) is configured. Attackers can send a client probe that fails the SOCKS version check to trigger a reply containing uninitialized bytes from the sin structure, exposing high bytes of a userspace pointer that weakens ASLR protections.
Title 3proxy 0.9.7 - 1.0.1 Uninitialized Stack Memory Disclosure via SOCKS4
Weaknesses CWE-908
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'}

cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N'}

Subscriptions

3proxy 3proxy
cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-10-27T01:30:42.993Z

Reserved: 2026-10-12T15:52:36.682Z

Link: CVE-2026-109438

cve-icon Vulnrichment

Updated: 2026-10-15T19:02:20.623Z

cve-icon NVD

Status : Deferred

Published: 2026-10-14T16:17:36.783

Modified: 2026-10-16T18:25:45.343

Link: CVE-2026-109438

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-22T22:15:12Z

Weaknesses
  • CWE-908

    Use of Uninitialized Resource