CVE-2023-25403Public exploitNetwork attack vector

Account takeover via predictable JWT signing key

Published Mar 3, 2023 · Updated Mar 7, 2025

Authentication bypass in CleverStupidDog yf-exam 1.8.0 allows remote attackers to obtain another user's access via a forged JWT. The JWT sign method accepts a username claim and signs it with an HMAC key deterministically derived by hashing that username and the current month twice. Knowledge of a target username and the current month is sufficient to mint a 24-hour token and enter that account's protected interface without its password.

CVSS severity7.5
High
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in CleverStupidDog yf-exam 1.8.0 allows remote attackers to obtain another user's access via a forged JWT. The JWT sign method accepts a username claim and signs it with an HMAC key deterministically derived by hashing that username and the current month twice. Knowledge of a target username and the current month is sufficient to mint a 24-hour token and enter that account's protected interface without its password.

The record

CVE
CVE-2023-25403
Published
Mar 3, 2023
Updated
Mar 7, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-639, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 3, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 7, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-639Authorization Bypass Through User-Controlled Key
T1078Valid Accounts

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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