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CVE Vulnerabilities

CVE-2018-19518

Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

Published: Nov 25, 2018 | Modified: Nov 07, 2023
CVSS 3.x
7.5
HIGH
Source:
NVD
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 2.x
8.5 HIGH
AV:N/AC:M/Au:S/C:C/I:C/A:C
RedHat/V2
RedHat/V3
8.1 MODERATE
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Ubuntu
MEDIUM
Additional information
NVDhttps://nvd.nist.gov/vuln/detail/CVE-2018-19518
CWEhttps://cwe.mitre.org/data/definitions/88.html

University of Washington IMAP Toolkit 2007f on UNIX, as used in imap_open() in PHP and other products, launches an rsh command (by means of the imap_rimap function in c-client/imap4r1.c and the tcp_aopen function in osdep/unix/tcp_unix.c) without preventing argument injection, which might allow remote attackers to execute arbitrary OS commands if the IMAP server name is untrusted input (e.g., entered by a user of a web application) and if rsh has been replaced by a program with different argument semantics. For example, if rsh is a link to ssh (as seen on Debian and Ubuntu systems), then the attack can use an IMAP server name containing a -oProxyCommand argument.

Weakness

The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string.

Affected Software

Name Vendor Start Version End Version
Php Php 5.6.0 (including) 5.6.38 (including)
Php Php 7.0.0 (including) 7.0.32 (including)
Php Php 7.1.0 (including) 7.1.24 (including)
Php Php 7.2.0 (including) 7.2.12 (including)
Php-imap Ubuntu trusty *
Php7.0 Ubuntu upstream *
Php7.0 Ubuntu xenial *
Php7.2 Ubuntu bionic *
Php7.2 Ubuntu cosmic *
Php7.2 Ubuntu disco *
Php7.2 Ubuntu upstream *
Php7.3 Ubuntu upstream *
Uw-imap Ubuntu bionic *
Uw-imap Ubuntu cosmic *
Uw-imap Ubuntu disco *
Uw-imap Ubuntu trusty *
Uw-imap Ubuntu trusty/esm *
Uw-imap Ubuntu upstream *
Uw-imap Ubuntu xenial *

Extended Description

When creating commands using interpolation into a string, developers may assume that only the arguments/options that they specify will be processed. This assumption may be even stronger when the programmer has encoded the command in a way that prevents separate commands from being provided maliciously, e.g. in the case of shell metacharacters. When constructing the command, the developer may use whitespace or other delimiters that are required to separate arguments when the command. However, if an attacker can provide an untrusted input that contains argument-separating delimiters, then the resulting command will have more arguments than intended by the developer. The attacker may then be able to change the behavior of the command. Depending on the functionality supported by the extraneous arguments, this may have security-relevant consequences.

Potential Mitigations

  • 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.
  • When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
  • Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
  • Inputs should be decoded and canonicalized to the application’s current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control.
  • Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.

References

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