Weakness (CWE)
CWE-159: Improper Handling of Invalid Use of Special Elements
The product does not properly filter, remove, quote, or otherwise manage the invalid use of special elements in user-controlled input, which could cause adverse effect on its behavior and integrity.
How to prevent it (4 mitigations)
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Developers should anticipate that special elements will be injected/removed/manipulated in the input vectors of their software system. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
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Implementation
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.
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Implementation
While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection (CWE-88).
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Implementation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
Source: MITRE CWE-159
13 results · Feed
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High 7.2
Tornado has incomplete validation of cookie attributes
In Tornado before 6.5.5, cookie attribute injection could occur because the domain, path, and samesite arguments to .RequestHandler.set_cookie were not checked for crafted characters.
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Medium 5.9
SuiteCRM has blind XSS in return_id parameter
SuiteCRM is an open-source, enterprise-ready Customer Relationship Management (CRM) software application. Prior to versions 7.15.1 and 8.9.3, the value of the return_id request parameter is copied into the value of an HTML tag attribute which is an event hand…
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Medium 5.5CVE-2026-2636 Public exploit
Denial of Service in Microsoft OS
This vulnerability is caused by a CWE‑159: "Improper Handling of Invalid Use of Special Elements" weakness, which leads to an unrecoverable inconsistency in the CLFS.sys driver. This condition forces a call to the KeBugCheckEx function, allowing an unprivileg…
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Low 3.6CVE-2025-61984 Public exploit
ssh in OpenSSH before 10.1 allows control characters in usernames that originate from certain possibly untrusted source…
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Low 1.7
risc0-ethereum-contracts allows invalid commitment with digest value of zero to be accepted by Steel.validateCommitment
RISC Zero is a zero-knowledge verifiable general computing platform, with Ethereum integration. The risc0-ethereum repository contains Solidity verifier contracts, Steel EVM view call library, and supporting code. Prior to versions 2.1.1 and 2.2.0, the `Steel…
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Medium 5.3
Failure to check for packets from the broadcast address allows potential DDoS amplification attack in Meshtastic firmware
Meshtastic firmware is a device firmware for the Meshtastic project. The Meshtastic firmware does not check for packets claiming to be from the special broadcast address (0xFFFFFFFF) which could result in unexpected behavior and potential for DDoS attacks on …
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Medium 5.3
Special characters break path parsing in XML functions
In PHP versions 7.3.x below 7.3.33, 7.4.x below 7.4.26 and 8.0.x below 8.0.13, certain XML parsing functions, like simplexml_load_file(), URL-decode the filename passed to them. If that filename contains URL-encoded NUL character, this may cause the function …
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Medium 5.5
An incorrect handling of a special element in Busybox's ash applet leads to denial of service when processing a crafted…
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Medium 5.3
Host Header Injection allowing web cache poisoning attacks
Failure to Sanitize host header value on output in the GateManager Web server could allow an attacker to conduct web cache poisoning attacks. This issue affects Secomea GateManager all versions prior to 9.3
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High 7.5
Junos OS: Kernel crash (vmcore) or FPC crash due to mbuf leak
On Juniper Networks Junos OS devices, a stream of TCP packets sent to the Routing Engine (RE) may cause mbuf leak which can lead to Flexible PIC Concentrator (FPC) crash or the system to crash and restart (vmcore). This issue can be trigged by IPv4 or IPv6 an…
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High 7.5
Junos OS and Junos OS Evolved: RPD crash when processing a specific BGP packet
On Juniper Networks Junos OS and Junos OS Evolved devices, processing a specific BGP packet can lead to a routing process daemon (RPD) crash and restart. This issue can occur even before the BGP session with the peer is established. Repeated receipt of this s…
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High 7.5
Junos OS and Junos OS Evolved: RPD crash while processing a specific BGP update information.
On Juniper Networks Junos OS and Junos OS Evolved devices, processing a specific UPDATE for an EBGP peer can lead to a routing process daemon (RPD) crash and restart. This issue occurs only when the device is receiving and processing the BGP UPDATE for an EBG…
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Unscored —
PrinterLogic Print Management Software does not sanitize special characters
The PrinterLogic Print Management software, versions up to and including 18.3.1.96, does not sanitize special characters allowing for remote unauthorized changes to configuration files. An unauthenticated attacker may be able to remotely execute arbitrary cod…