CVE-2025-43931Network attack vector

Account takeover via Host-poisoned password reset

Published Jul 7, 2025 · Updated Jul 8, 2025

Weak password recovery in flask-boilerplate through a170e7c allows remote attackers to take over accounts via password reset. The forgot() route passes _external=True to url_for(), so Flask builds the emailed reset URL from the untrusted Host header when SERVER_NAME is absent. A deployment must leave SERVER_NAME unset and accept attacker-controlled Host values; use of the poisoned reset link exposes its token and permits replacement of the victim account's password.

CVSS severity9.8
Critical
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Weak password recovery in flask-boilerplate through a170e7c allows remote attackers to take over accounts via password reset. The forgot() route passes _external=True to url_for(), so Flask builds the emailed reset URL from the untrusted Host header when SERVER_NAME is absent. A deployment must leave SERVER_NAME unset and accept attacker-controlled Host values; use of the poisoned reset link exposes its token and permits replacement of the victim account's password.

The record

CVE
CVE-2025-43931
Published
Jul 7, 2025
Updated
Jul 8, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-640, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

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.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-640Weak Password Recovery Mechanism for Forgotten Password
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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo