web: Improper Neutralization of CRLF Sequences
CVE-2025-59151 is a high-severity improper neutralization of CRLF sequences vulnerability in web from Pi-hole, with a CVSS 3.1 base score of 8.2 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected web versions: < 6.3. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.44% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Web Interface to 6.3 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Pi-hole | web | < 6.3 | Not stated |
| Pi-hole | Web Interface | before 6.3 | 6.3 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- HighData or code can be modified at will.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L. Scored by CNA (github.com).
Official description
Pi-hole Admin Interface is a web interface for managing Pi-hole, a network-level advertisement and internet tracker blocking application. Pi-hole Admin Interface before 6.3 is vulnerable to Carriage Return Line Feed (CRLF) injection. When a request is made to a file ending with the .lp extension, the application performs a redirect without properly sanitizing the input. An attacker can inject carriage return and line feed characters (%0d%0a) to manipulate both the headers and the content of the HTTP response. This enables the injection of arbitrary HTTP response headers, potentially leading to session fixation, cache poisoning, and the weakening or bypassing of browser-based security mechanisms such as Content Security Policy or X-XSS-Protection. This vulnerability is fixed in 6.3.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of CRLF Sequences
The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.
How developers prevent this class of flaw
- Appropriately filter or quote CRLF sequences in user-controlled input.
More Improper Neutralization of CRLF Sequences vulnerabilities (CWE-93)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in web
- 9.8 Critical severity
- 8.8 High severity
Recent Improper Neutralization of CRLF Sequences vulnerabilities
- 8.8 High severity
- 7.2 High severity
- 8.7 High severity
- 7.7 High severity
- 9.3 Critical severity
- 7.1 High severity
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