php-imap: Improper Limitation of a Pathname to a Restricted Directory
CVE-2023-35169 is a critical-severity improper limitation of a pathname to a restricted directory vulnerability in php-imap from Webklex, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected php-imap versions: < 5.3.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 3.19% chance of exploitation within 30 days, higher than 88% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of php-imap you run against the affected versions below, and install the vendor's latest release.
- 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
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
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.0 | Critical | CNA (github.com) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
PHP-IMAP is a wrapper for common IMAP communication without the need to have the php-imap module installed / enabled. Prior to version 5.3.0, an unsanitized attachment filename allows any unauthenticated user to leverage a directory traversal vulnerability, which results in a remote code execution vulnerability. Every application that stores attachments with `Attachment::save()` without providing a `$filename` or passing unsanitized user input is affected by this attack. An attacker can send an email with a malicious attachment to the inbox, which gets crawled with `webklex/php-imap` or `webklex/laravel-imap`. Prerequisite for the vulnerability is that the script stores the attachments without providing a `$filename`, or providing an unsanitized `$filename`, in `src/Attachment::save(string $path, string $filename = null)`. In this case, where no `$filename` gets passed into the `Attachment::save()` method, the package would use a series of unsanitized and insecure input values from the mail as fallback. Even if a developer passes a `$filename` into the `Attachment::save()` method, e.g. by passing the name or filename of the mail attachment itself (from email headers), the input values never get sanitized by the package. There is also no restriction about the file extension (e.g. ".php") or the contents of a file. This allows an attacker to upload malicious code of any type and content at any location where the underlying user has write permissions. The attacker can also overwrite existing files and inject malicious code into files that, e.g. get executed by the system via cron or requests. Version 5.3.0 contains a patch for this issue.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Limitation of a Pathname to a Restricted Directory
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
How developers prevent this class of flaw
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
- Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.
More Improper Limitation of a Pathname to a Restricted Directory vulnerabilities (CWE-22)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
Other references
Recent Improper Limitation of a Pathname to a Restricted Directory vulnerabilities
- 8.1 High severity
- 9.8 Critical severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 9.8 Critical severity
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