CVE-2026-81738Network attack vector

Memory corruption via DOMAIN-SEARCH length undercount

Published Sep 7, 2026 · Updated Sep 8, 2026

Out-of-bounds write in OpenVPN 2.5.0 through 2.7.6 on Windows allows attackers to corrupt memory via crafted DOMAIN-SEARCH entries. In write_dhcp_search_str(), the length guard undercounts every encoded entry by one byte before writing to a 256-byte stack buffer. A Windows client must use tap-windows6 and accept pushed DHCP options from a server; the published materials document a one-byte overwrite but no crash or code-execution outcome.

CVSS severity2.3
Low
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in OpenVPN 2.5.0 through 2.7.6 on Windows allows attackers to corrupt memory via crafted DOMAIN-SEARCH entries. In write_dhcp_search_str(), the length guard undercounts every encoded entry by one byte before writing to a 256-byte stack buffer. A Windows client must use tap-windows6 and accept pushed DHCP options from a server; the published materials document a one-byte overwrite but no crash or code-execution outcome.

The record

CVE
CVE-2026-81738
Published
Sep 7, 2026
Updated
Sep 8, 2026
Vendor
OpenVPN Inc.
Product
OpenVPN
Classifications
CWE-787, CWE-121, CWE-193
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 7, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.5.0 <=2.7.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenVPN Inc. · OpenVPNversion=2.5.0 <=2.7.6

Published CVSS scores

5.4Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
2.3OpenVPN Inc.CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:L/VA:L/SC:N/SI:L/SA:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-121Stack-based Buffer Overflow
CWE-193Off-by-one Error

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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