CVE-2026-109438: 3proxy 0.9.7 - 1.0.1 Uninitialized Stack Memory Disclosure via SOCKS4

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-14 · updated 2026-10-27
Weakness: CWE-908

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.

Affected products

3proxy: from 0.9.7 through 1.0.1

References

https://github.com/3proxy/3proxy/commit/206c923d6cd433bd2e7196375442650c328b8bfa
https://www.vulncheck.com/advisories/3proxy-uninitialized-stack-memory-disclosure-via-socks4

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