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PyJWT CVE-2026-102268

| EUVDEUVD-2026-88535 CRITICAL
Improper Verification of Cryptographic Signature (CWE-347)
2026-09-28 GitHub_M GHSA-ffc3-869f-jxw9
Authentication Bypass Python Jwt Attack Pyjwt Jpadilla
9.1
CVSS 3.1 · Vendor: GitHub_M
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Severity by source

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

Network token submission needs no auth (PR:N/AV:N), but the vulnerable mixed-algorithm config plus crafting a loader-accepted mutated PEM raises complexity to AC:H; forgery breaks integrity/auth with data-access confidentiality impact, no availability effect.

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
7.4 HIGH
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

Attack Vector
Network
Attack Complexity
Low
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 - 21:01 vuln.today
CVE Published
Sep 28, 2026 - 20:26 cve.org
CRITICAL 9.1

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 18 pypi packages depend on pyjwt (16 direct, 2 indirect)

Ecosystem-wide dependent count for version 2.14.0.

DescriptionCVE.org

PyJWT is a Python implementation of JSON Web Token standards. Prior to 2.14.0, is_pem_format in jwt/utils.py is affected because is_pem_format does not recognize every PEM representation accepted by the cryptography loader. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a mutated public-key PEM as raw key bytes. As a result, HMACAlgorithm.prepare_key treats the unrecognized asymmetric public key 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 2

News 13 New Python Vulnerabilities - 2 Critical, 11 High, 2 With POC Sep 29, 2026 News Critical Authentication Bypass in PyJWT before 2.14.0 - CVE-2026-102268 Sep 28, 2026

AnalysisAI

Signature forgery in PyJWT before 2.14.0 allows an attacker who knows a target's asymmetric public key to forge HMAC-authenticated JWTs when the application mixes HMAC and asymmetric algorithms and passes asymmetric public-key PEM bytes into HMAC verification. The flaw is in is_pem_format in jwt/utils.py, which fails to recognize all PEM formatting variants accepted by the cryptography loader, causing HMACAlgorithm.prepare_key to treat a mutated public-key PEM as an HMAC secret. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Exploitation requires the target application to (1) use PyJWT prior to 2.14.0, (2) mix HMAC and asymmetric algorithms in verification, and (3) supply an asymmetric public-key PEM as raw key bytes to HMACAlgorithm - a specific and non-default deployment pattern, the same dangerous configuration underlying classic RS256-to-HS256 key confusion. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment This is a genuine algorithm-confusion / signature-forgery flaw (CWE-347) in PyJWT, an extremely widely deployed Python JWT library, so the theoretical blast radius is large. … 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 Upgrade PyJWT to 2.14.0, the vendor-released patch that fixes is_pem_format (release: https://github.com/jpadilla/pyjwt/releases/tag/2.14.0; advisory: https://github.com/jpadilla/pyjwt/security/advisories/GHSA-ffc3-869f-jxw9). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, inventory every Python service and container image that depends on PyJWT, and for each one inspect the jwt.decode and jwt.encode call sites to determine whether both HMAC (HS256/HS384/HS512) and asymmetric (RS*/ES*/PS*) algorithms are accepted and whether raw PEM public-key bytes are ever supplied as the verification key; flag any service matching that pattern as exposed, and immediately harden the call sites by passing an explicit algorithms allowlist to jwt.decode (for example algorithms=["RS256"]), never letting the algorithm be inferred from the token header, and by supplying key objects from the cryptography library rather than raw PEM bytes. …

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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 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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CVE-2026-102268 vulnerability details – vuln.today
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