Advisory severityMedium5.3Red Hat Linux

Medium [CVE-2026-11771] Denial of Service via crafted NTLM proxy response

This medium-severity Red Hat Linux advisory covers CVE-2026-11771.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-11771 Source published Jul 30, 2026Source updated Jul 30, 2026

VulniPulse record published Aug 1, 2026Record updated Aug 11, 2026

CVE-2026-11771

Affected products & platforms

Red Hat LinuxUnclassified

Open source advisory

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Summary

OpenVPN version 2.1.0 through 2.6.20 and 2.7_alpha1 through 2.7.4 allows attackers via an off-by-one buffer write in the NTLM proxy authentication to potentially cause a crash via a crafted NTLM response from a malicious proxy server A flaw was found in OpenVPN.

A remote attacker could exploit an off-by-one buffer write vulnerability during NTLM (NT LAN Manager) proxy authentication. By sending a specially crafted NTLM response from a malicious proxy server, the attacker could cause the OpenVPN client to crash, leading to a denial of service.

Exploitation requires a client to connect through a malicious NTLM proxy server, which can then send a specially crafted response. The necessity of user interaction with a compromised proxy limits the overall risk.

Red Hat severity: Moderate — CVSS 5.3 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H). Weakness: CWE-787.

Affected versions

2.1.0
2.6.20
2.7.4

Official advisory · high-confidence parse· fetched 9 days ago·verify at source

Fixed versions

No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.

Official advisory · high-confidence parse· fetched 9 days ago·verify at source

Mitigation

The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.

Official advisory · high-confidence parse· fetched 9 days ago·verify at source

Discussion(0)

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