CVE-2021-28373Network attack vector

Unauthenticated account access via OTP-only validation

Published Mar 13, 2021 · Updated Aug 3, 2024

Authentication bypass in Tiny Tiny RSS before 2021-03-12 allows remote attackers to access user accounts with an OTP but no password. The auth_internal plugin's authenticate() method accepted UserHelper::check_otp() alone and returned the matched user ID without calling check_password(). Two-factor authentication had to be enabled and a valid OTP supplied; the flaw affected the continuously deployed master branch only briefly.

CVSS severity7.5
High
EPSS probability0.93%
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 Tiny Tiny RSS before 2021-03-12 allows remote attackers to access user accounts with an OTP but no password. The auth_internal plugin's authenticate() method accepted UserHelper::check_otp() alone and returned the matched user ID without calling check_password(). Two-factor authentication had to be enabled and a valid OTP supplied; the flaw affected the continuously deployed master branch only briefly.

The record

CVE
CVE-2021-28373
Published
Mar 13, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-863, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/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.

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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-863Incorrect Authorization
T1078Valid Accounts

Public exploit references

No public exploit references are available in this record.

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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