CVE-2026-11771: openvpn Stack-based Buffer Overflow
CVSS: 7.5v3.1HighAnalyzed
AliasesALPINE-CVE-2026-11771UBUNTU-CVE-2026-11771DEBIAN-CVE-2026-11771
Published 30-07-2026Last modified 30-07-2026
Vulnerability summary
CVE-2026-11771 is a high (CVSS 7.5) Stack-based Buffer Overflow vulnerability in openvpn. EPSS estimates a 0.68% chance of exploitation in the next 30 days, higher than 51.9% of scored vulnerabilities.
CVSS score
7.5/10
010
High · v3.1 (NVD)EPSS score
0.68%
0%100%
Low · +0.31 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 3 · Related 3Timeline
- 30-07-2026PublishedVulnerability first disclosed.
- 30-07-2026Last modifiedVulnerability information updated.
Description
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
CVSS metrics
7 scores · 5 sources · 2 versionsHigh 7.0Preferred score · CVE.org (CNA)
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:HSourcesAll 3 agree
- OSV · UbuntuEcosystem advisory · calculated7.0HighCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
- NVDNIST7.0HighCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
High 7.5Preferred score · NVD (NIST)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSourcesAll 4 agree
- OSV · AlpineEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.68%
Chance of exploitation in the next 30 days
Percentile
52%
Versus all other CVEs
30-day change
+0.31 pp
From 0.38% on 21-09-2026
21-09-202621-10-2026
EPSS score0.68%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-121Stack-based Buffer OverflowA stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
- CWE-193Off-by-one ErrorA product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
- CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.
Affected systems
Alpine1 product
- openvpn≥ 2.1.0, < 2.7.5-r0
Debian1 product
- openvpn< 2.6.14-0+deb12u2 | < 2.6.14-1+deb13u3 | < 2.7.5-1
Openvpn1 product
- openvpn≥ 2.1.0, ≤ 2.6.20 | ≥ 2.7_alpha1, ≤ 2.7.4 | ≥ 2.1.0, < 2.6.21 | ≥ 2.7, < 2.7.5
Ubuntu1 product
- openvpn< 2.6.19-0ubuntu0.24.04.3 | All versions (No fix recorded) | < 2.7.0-1ubuntu1.2
4 vendors · 4 products
References
8 links- community.openvpn.net/ReleaseHistoryRelease Notes
- community.openvpn.net/ReleaseHistoryRelease Notes
