VulnerabilityPublished 18 Nov 2025Updated 19 Nov 2025

CVE-2025-63828: BackdropCms · Host Header Injection

Affects BackdropCmsSource CVE Database V5

Not known to be exploited · CVSS 6.1 Medium.

Data as of 26 Oct 2026, 12:29 UTC

CVSS 3.1 base score

6.1Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 13% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Changed
Confidentiality: Low
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Nov 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
GitHubmertdurum06/BackdropCms`pkg:github/mertdurum06/BackdropCms`Other threats	Affected =1.32.1	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Immediately implement strict validation and sanitization of the Host header in all HTTP requests, especially those involved in password reset workflows.
Configure the application or web server to enforce a whitelist of allowed Host headers to prevent arbitrary host values.
Implement strict redirect policies that only allow redirects to trusted domains or relative paths.
Monitor web server and application logs for unusual Host header values or redirect patterns indicative of exploitation attempts.
Educate users to be cautious of password reset emails and verify URLs before clicking.
Deploy Web Application Firewalls (WAFs) with rules to detect and block Host header injection attempts.
Once available, promptly apply official patches or updates from Backdrop CMS addressing this vulnerability.
Conduct security testing and code reviews focusing on header validation and redirect handling.
Consider multi-factor authentication to reduce the impact of session hijacking.
Isolate critical systems and limit exposure of password reset endpoints where feasible.

Description

Host Header Injection vulnerability in Backdrop CMS 1.32.1 allows attackers to manipulate the Host header in password reset requests, leading to redirects to malicious domains and potential session hijacking via cookie injection.

Impact

For European organizations using Backdrop CMS 1.32.1, this vulnerability poses a risk of user session compromise and phishing attacks via malicious redirects. Attackers could hijack user sessions by injecting cookies, potentially gaining unauthorized access to sensitive user accounts or administrative functions. This could lead to data breaches, unauthorized changes, or further exploitation within the organization’s web infrastructure. The impact is particularly critical for organizations with large user bases or those handling sensitive personal or financial data. Public-facing password reset functionalities increase exposure. Additionally, reputational damage and regulatory consequences under GDPR could arise if user data is compromised. The medium severity score reflects that while exploitation requires user interaction, the ease of remote exploitation and the potential for chained attacks elevate the risk. Organizations relying on Backdrop CMS for their websites or intranet portals should consider this a significant threat to their web security posture.

CWE-601URL Redirection to Untrusted Site ('Open Redirect') (opens in a new tab)
Base weaknessLikelihood of exploit: LowOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design
Use an intermediate disclaimer page that provides the user with a clear warning that they are leaving the current site. Implement a long timeout before the redirect occurs, or force the user to click on the link. Be careful to avoid XSS problems (CWE-79) when generating the disclaimer page.
Architecture and Design · Enforcement by Conversion
When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
OWASP Cheat Sheets
Mass Assignment (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V5.1.5 (opens in a new tab)
Attack patterns
Cross-Site Flashing (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Nov 2025, 19:11 UTC

WeaknessesCWE-601

Technical details

References

Community reviews

Related threats