CVE-2025-43933Network attack vector

Account takeover via Host header reset poisoning

Published Jul 7, 2025 · Updated Jul 8, 2025

Host header injection in fblog through 983bede allows remote attackers to take over accounts through the password reset feature. The resetPassword.html template calls url_for with _external=True while SERVER_NAME is unset, so Flask builds the reset URL from an attacker-controlled Host header. An unauthenticated attacker can direct the emailed reset link to an attacker-controlled domain, but account takeover requires the recipient to open the poisoned link and disclose the token.

CVSS severity9.8
Critical
EPSS probability0.37%
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 fblog through 983bede allows remote attackers to take over accounts through the password reset feature. The resetPassword.html template calls url_for with _external=True while SERVER_NAME is unset, so Flask builds the reset URL from an attacker-controlled Host header. An unauthenticated attacker can direct the emailed reset link to an attacker-controlled domain, but account takeover requires the recipient to open the poisoned link and disclose the token.

The record

CVE
CVE-2025-43933
Published
Jul 7, 2025
Updated
Jul 8, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-472, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 7, 2025CVE publishedPublication date reported by the CVE source.
  2. Jul 8, 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

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-472External Control of Assumed-Immutable Web Parameter
T1190Exploit Public-Facing Application

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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