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python-cryptography EUVDEUVD-2026-52448

| CVE-2026-69248 MEDIUM
Improper Certificate Validation (CWE-295)
2026-08-03 GitHub_M GHSA-m2h6-j472-rp4c
Python Information Disclosure Cryptography Pyca
6.9
CVSS 4.0 · Vendor: GitHub_M
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Severity by source

Vendor (GitHub_M) PRIMARY
6.9 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/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
vuln.today AI
6.5 MEDIUM

AV:N as the flaw is triggered by presenting crafted certificates over the network; AC:H reflects the specific prerequisite of a constrained sub-CA with permittedSubtrees; I:H for certificate trust bypass enabling domain impersonation.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N
SUSE
5.4 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
Red Hat
7.4 MEDIUM
qualitative

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

4
Patch available
Aug 03, 2026 - 22:17 EUVD
Source Code Evidence Fetched
Aug 03, 2026 - 22:06 vuln.today
Analysis Generated
Aug 03, 2026 - 22:06 vuln.today
CVE Published
Aug 03, 2026 - 21:21 cve.org
MEDIUM 6.9

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 468 pypi packages depend on cryptography (259 direct, 209 indirect)

Ecosystem-wide dependent count for version 49.0.0.

DescriptionCVE.org

cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. Prior to 49.0.0, if an intermediate constrained CA permits the DNS name foo.example.com, and the leaf certificate has a wildcard in its DNS SAN of *.example.com, python-cryptography's verifier accepts which allows escaping outside of the permitted names. The core issue is in DNSConstraint::matches, where a wildcard pattern was treated as matching a more-specific permitted constraint even though *.example.com can expand to sibling names such as bar.example.com outside foo.example.com. This allows acceptance of an invalid certificate chain. This issue is fixed in 49.0.0.

AnalysisAI

Wildcard DNS SAN matching in python-cryptography's X.509 chain verifier prior to 49.0.0 allows a leaf certificate bearing *.example.com to satisfy a constrained intermediate CA's permittedSubtrees restriction of foo.example.com, enabling scope escape to sibling domains such as bar.example.com. Applications relying on the PolicyBuilder/Store verification API are exposed to acceptance of invalid certificate chains that should be rejected per RFC 5280 §4.2.1.10. A public proof-of-concept is confirmed in the GHSA advisory; the vulnerability is not in the CISA KEV catalog, but the CVSS 4.0 E:P modifier reflects the POC's availability.

Technical ContextAI

The flaw resides in the Rust-backed crate cryptography-x509-verification, specifically DNSConstraint::matches in src/rust/cryptography-x509-verification/src/types.rs (CPE: cpe:2.3:a:pyca:cryptography:*:*:*:*:*:*:*:*). RFC 5280 §4.2.1.10 Name Constraints define permittedSubtrees and excludedSubtrees, each requiring distinct matching semantics for wildcard DNS SANs. A wildcard like *.example.com represents a set of single-label expansions, so a permittedSubtrees constraint of foo.example.com cannot contain all names the wildcard expands to - yet the buggy matches() function applied the same logic to both subtree kinds, incorrectly accepting the wildcard as satisfying the narrower constraint. The fix, merged in PR #14888 and commit 4d035a4225965edeffd312079a510ef25fcfdcb2, introduces a SubtreeKind enum dispatching to permits() (containment semantics for permittedSubtrees) versus excludes() (overlap semantics for excludedSubtrees). CWE-295 (Improper Certificate Validation) precisely captures the root cause: the verifier's logic diverges from the RFC's required semantics.

RemediationAI

Upgrade to python-cryptography 49.0.0 or later via pip install 'cryptography>=49.0.0'. The fix is delivered in commit 4d035a4225965edeffd312079a510ef25fcfdcb2 (https://github.com/pyca/cryptography/commit/4d035a4225965edeffd312079a510ef25fcfdcb2) and PR #14888 (https://github.com/pyca/cryptography/pull/14888). If an immediate upgrade is not feasible, applications that require Name Constraints enforcement should switch certificate verification to OpenSSL's own engine rather than using the PolicyBuilder/Store path - this eliminates the vulnerable code path entirely, though it requires refactoring the verification call site. Alternatively, applications can add an explicit pre-verification check that rejects any leaf certificate whose DNS SANs contain wildcard entries when Name Constraints are present in the issuing chain; this is conservative and may reject some valid certificates, but eliminates the bypass. Generic network filtering provides no mitigation because the flaw is in library logic, not a network-accessible endpoint.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Not-Affected
SUSE Linux Enterprise Desktop 15 SP7 Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Not-Affected
SUSE Linux Enterprise Micro 5.3 Not-Affected

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EUVD-2026-52448 vulnerability details – vuln.today
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