CVE-2026-48526Public exploitNetwork attack vector

Unauthenticated token forgery via public-key JWK confusion

Published May 28, 2026 · Updated May 28, 2026

Algorithm confusion in PyJWT before 2.13.0 allows remote attackers to forge JWTs and impersonate arbitrary users. HMACAlgorithm.prepare_key rejects PEM and SSH public keys but treats raw JSON JWK text as an HMAC secret, so an issuer's public JWK validates attacker-chosen HS256 claims. Exploitation requires an application that allows both HMAC and asymmetric algorithms and passes a raw JSON JWK as the verification key, enabling identity and role impersonation.

CVSS severity7.4
High
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Algorithm confusion in PyJWT before 2.13.0 allows remote attackers to forge JWTs and impersonate arbitrary users. HMACAlgorithm.prepare_key rejects PEM and SSH public keys but treats raw JSON JWK text as an HMAC secret, so an issuer's public JWK validates attacker-chosen HS256 claims. Exploitation requires an application that allows both HMAC and asymmetric algorithms and passes a raw JSON JWK as the verification key, enabling identity and role impersonation.

The record

CVE
CVE-2026-48526
Published
May 28, 2026
Updated
May 28, 2026
Vendor
Jose Padilla
Product
PyJWT
Classifications
CWE-287, CWE-347, T1606
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 28, 2026CVE publishedPublication date reported by the CVE source.
  2. May 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.13.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Jose Padilla · PyJWTversion=< 2.13.0

Published CVSS scores

7.4GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-287Improper Authentication
CWE-347Improper Verification of Cryptographic Signature
T1606Forge Web Credentials

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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