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PyJWT EUVDEUVD-2026-88539

| CVE-2026-102271 HIGH
Improper Verification of Cryptographic Signature (CWE-347)
2026-09-28 GitHub_M GHSA-p4g4-x82p-q773
Authentication Bypass Python Jwt Attack Pyjwt Jpadilla
7.4
CVSS 3.1 · Vendor: GitHub_M
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Severity by source

Vendor (GitHub_M) PRIMARY
7.4 HIGH
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
vuln.today AI
7.4 HIGH

Network-reachable and unauthenticated (PR:N) since only the public key is needed, but AC:H because it depends on a mixed-algorithm + DER-key-as-secret misconfiguration; forged tokens grant impersonation so C:H/I:H, no availability impact.

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

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Lifecycle Timeline

6
POC Analysis Generated
Sep 28, 2026 - 23:24 vuln.today
Patch available
Sep 28, 2026 - 22:02 EUVD
Metadata Corrected
Sep 28, 2026 - 21:40 vuln.today
tag: Authentication Bypass added
Metadata Corrected
Sep 28, 2026 - 21:40 vuln.today
tag: Information Disclosure removed
Analysis Generated
Sep 28, 2026 - 21:02 vuln.today
CVE Published
Sep 28, 2026 - 20:31 cve.org
HIGH 7.4

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 275 pypi packages depend on pyjwt (199 direct, 76 indirect)

Ecosystem-wide dependent count for version 2.4.0.

DescriptionCVE.org

PyJWT is a Python implementation of JSON Web Token standards. From 2.4.0 until 2.14.0, PyJWT HMACAlgorithm.prepare_key is affected because asymmetric-key guard relies on textual markers that are absent from DER encoding. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a DER public key as the shared verification key. As a result, PyJWT uses public DER bytes as an HMAC secret. Consequently, an attacker who knows the public key can forge authenticated HMAC tokens. This issue is fixed in version 2.14.0.

Articles & Coverage 1

News 13 New Python Vulnerabilities - 2 Critical, 11 High, 2 With POC Sep 29, 2026

AnalysisAI

Signature forgery in the PyJWT Python library (versions 2.4.0 through 2.13.x) lets a remote, unauthenticated attacker mint forged HMAC tokens whenever an application is misconfigured to accept both HMAC and asymmetric algorithms and passes a DER-encoded public key as the shared verification secret. PyJWT's HMACAlgorithm.prepare_key only rejected PEM- and SSH-formatted asymmetric keys using textual markers, so a DER public key (SubjectPublicKeyInfo, PKCS1, or a DER x509 certificate) slipped through and its public bytes were used directly as the HMAC secret - meaning anyone who knows the public key can sign valid tokens. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Exploitation requires all of: (1) the application configures PyJWT to accept BOTH HMAC and asymmetric algorithms (the classic algorithm-confusion precondition); (2) the application supplies a DER-encoded public key (SubjectPublicKeyInfo, PKCS1, or a DER x509 certificate) as the shared verification key rather than a PEM/SSH-formatted key - PEM and SSH keys were already caught by the pre-existing textual guard; and (3) the attacker knows the public key (which, being public, is a low bar). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment This is a genuine but conditionally-triggered signature-forgery / algorithm-confusion flaw (CWE-347), not a high-CVSS-but-low-impact issue in the abstract - yet its real-world reachability is narrow. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Vendor-released patch: upgrade PyJWT to version 2.14.0, which adds the _is_der_key() check that rejects DER public keys and DER x509 certificates passed to HMACAlgorithm.prepare_key (see https://github.com/jpadilla/pyjwt/releases/tag/2.14.0 and advisory https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, inventory every Python service and dependency using PyJWT 2.4.0 through 2.13.x and flag any jwt.decode call that does not pin an explicit algorithms allowlist, or that accepts HMAC and asymmetric algorithms (for example HS256 alongside RS256 or ES256) against the same key material; treat those endpoints as potentially forgeable, enable verbose logging on token verification failures, and alert on unexpected token issuance. …

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 12 Not-Affected
SUSE Linux Enterprise Micro 5.5 Affected
SUSE Linux Enterprise Module for Basesystem 15 SP7 Affected
SUSE Linux Enterprise Module for Python 3 15 SP7 Affected

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EUVD-2026-88539 vulnerability details – vuln.today
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