CVE-2021-29251Network attack vector

Account takeover via poisoned password-reset link

Published Apr 1, 2021 · Updated Aug 3, 2024

Host-header injection in BTCPay Server before 1.0.7.1 allows remote authenticated users to take over accounts through poisoned reset links. The password-reset flow trusts attacker-controlled Host, X-Forwarded-Host, and X-Forwarded-For headers when constructing the emailed reset URL. Exposure requires Docker with SMTP and user registration enabled; takeover follows when the victim or an automated mail scanner visits the link.

CVSS severity6.5
Medium
EPSS probability0.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Host-header injection in BTCPay Server before 1.0.7.1 allows remote authenticated users to take over accounts through poisoned reset links. The password-reset flow trusts attacker-controlled Host, X-Forwarded-Host, and X-Forwarded-For headers when constructing the emailed reset URL. Exposure requires Docker with SMTP and user registration enabled; takeover follows when the victim or an automated mail scanner visits the link.

The record

CVE
CVE-2021-29251
Published
Apr 1, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1204.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1204.001User Execution: Malicious Link

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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