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Vulnerability Details :

CVE-2026-27448

Summary
Assigner-GitHub_M
Assigner Org ID-a0819718-46f1-4df5-94e2-005712e83aaa
Published At-17 Mar, 2026 | 23:24
Updated At-18 Mar, 2026 | 20:18
Rejected At-
Credits

pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback

pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 0.14.0 and prior to version 26.0.0, if a user provided callback to `set_tlsext_servername_callback` raised an unhandled exception, this would result in a connection being accepted. If a user was relying on this callback for any security-sensitive behavior, this could allow bypassing it. Starting in version 26.0.0, unhandled exceptions now result in rejecting the connection.

Vendors
-
Not available
Products
-
Metrics (CVSS)
VersionBase scoreBase severityVector
Weaknesses
Attack Patterns
Solution/Workaround
References
HyperlinkResource Type
EPSS History
Score
Latest Score
-
N/A
No data available for selected date range
Percentile
Latest Percentile
-
N/A
No data available for selected date range
Stakeholder-Specific Vulnerability Categorization (SSVC)
▼Common Vulnerabilities and Exposures (CVE)
cve.org
Assigner:GitHub_M
Assigner Org ID:a0819718-46f1-4df5-94e2-005712e83aaa
Published At:17 Mar, 2026 | 23:24
Updated At:18 Mar, 2026 | 20:18
Rejected At:
▼CVE Numbering Authority (CNA)
pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback

pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 0.14.0 and prior to version 26.0.0, if a user provided callback to `set_tlsext_servername_callback` raised an unhandled exception, this would result in a connection being accepted. If a user was relying on this callback for any security-sensitive behavior, this could allow bypassing it. Starting in version 26.0.0, unhandled exceptions now result in rejecting the connection.

Affected Products
Vendor
pyca
Product
pyopenssl
Versions
Affected
  • >= 0.14.0, < 26.0.0
Problem Types
TypeCWE IDDescription
CWECWE-636CWE-636: Not Failing Securely ('Failing Open')
Type: CWE
CWE ID: CWE-636
Description: CWE-636: Not Failing Securely ('Failing Open')
Metrics
VersionBase scoreBase severityVector
4.01.7LOW
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U
Version: 4.0
Base score: 1.7
Base severity: LOW
Vector:
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Configurations

Workarounds

Exploits

Credits

Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
https://github.com/pyca/pyopenssl/security/advisories/GHSA-vp96-hxj8-p424
x_refsource_CONFIRM
https://github.com/pyca/pyopenssl/commit/d41a814759a9fb49584ca8ab3f7295de49a85aa0
x_refsource_MISC
https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst#L27
x_refsource_MISC
Hyperlink: https://github.com/pyca/pyopenssl/security/advisories/GHSA-vp96-hxj8-p424
Resource:
x_refsource_CONFIRM
Hyperlink: https://github.com/pyca/pyopenssl/commit/d41a814759a9fb49584ca8ab3f7295de49a85aa0
Resource:
x_refsource_MISC
Hyperlink: https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst#L27
Resource:
x_refsource_MISC
▼Authorized Data Publishers (ADP)
CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Configurations

Workarounds

Exploits

Credits

Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
Information is not available yet
▼National Vulnerability Database (NVD)
nvd.nist.gov
Source:security-advisories@github.com
Published At:18 Mar, 2026 | 00:16
Updated At:23 Mar, 2026 | 18:10

pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 0.14.0 and prior to version 26.0.0, if a user provided callback to `set_tlsext_servername_callback` raised an unhandled exception, this would result in a connection being accepted. If a user was relying on this callback for any security-sensitive behavior, this could allow bypassing it. Starting in version 26.0.0, unhandled exceptions now result in rejecting the connection.

CISA Catalog
Date AddedDue DateVulnerability NameRequired Action
N/A
Date Added: N/A
Due Date: N/A
Vulnerability Name: N/A
Required Action: N/A
Metrics
TypeVersionBase scoreBase severityVector
Secondary4.01.7LOW
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/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
Primary3.15.3MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Type: Secondary
Version: 4.0
Base score: 1.7
Base severity: LOW
Vector:
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/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
Type: Primary
Version: 3.1
Base score: 5.3
Base severity: MEDIUM
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CPE Matches

pyopenssl
pyopenssl
>>pyopenssl>>Versions from 0.14(inclusive) to 26.0.0(exclusive)
cpe:2.3:a:pyopenssl:pyopenssl:*:*:*:*:*:*:*:*
Weaknesses
CWE IDTypeSource
CWE-636Primarysecurity-advisories@github.com
CWE ID: CWE-636
Type: Primary
Source: security-advisories@github.com
Evaluator Description

Evaluator Impact

Evaluator Solution

Vendor Statements

References
HyperlinkSourceResource
https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst#L27security-advisories@github.com
Release Notes
https://github.com/pyca/pyopenssl/commit/d41a814759a9fb49584ca8ab3f7295de49a85aa0security-advisories@github.com
Patch
https://github.com/pyca/pyopenssl/security/advisories/GHSA-vp96-hxj8-p424security-advisories@github.com
Vendor Advisory
Hyperlink: https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst#L27
Source: security-advisories@github.com
Resource:
Release Notes
Hyperlink: https://github.com/pyca/pyopenssl/commit/d41a814759a9fb49584ca8ab3f7295de49a85aa0
Source: security-advisories@github.com
Resource:
Patch
Hyperlink: https://github.com/pyca/pyopenssl/security/advisories/GHSA-vp96-hxj8-p424
Source: security-advisories@github.com
Resource:
Vendor Advisory

Change History

0
Information is not available yet

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