CVE-2026-48524Network attack vector

Authentication disruption via unbounded JWKS refreshes

Published May 28, 2026 · Updated May 28, 2026

Denial of service in PyJWKClient in PyJWT before 2.13.0 allows remote attackers to disrupt authentication via crafted JWT key IDs. The get_signing_key() path refreshes the JWKS for every unknown unverified kid without rate limiting, and fetch_data() clears cached keys after a request failure. Exploitation requires a failed JWKS fetch, so upstream throttling or transient errors determine whether sustained traffic reduces authentication availability.

CVSS severity3.7
Low
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in PyJWKClient in PyJWT before 2.13.0 allows remote attackers to disrupt authentication via crafted JWT key IDs. The get_signing_key() path refreshes the JWKS for every unknown unverified kid without rate limiting, and fetch_data() clears cached keys after a request failure. Exploitation requires a failed JWKS fetch, so upstream throttling or transient errors determine whether sustained traffic reduces authentication availability.

The record

CVE
CVE-2026-48524
Published
May 28, 2026
Updated
May 28, 2026
Vendor
Jose Padilla
Product
PyJWT
Classifications
CWE-755, CWE-460, T1499.003
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

3.7GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-755Improper Handling of Exceptional Conditions
CWE-460Improper Cleanup on Thrown Exception
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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