CVE-2026-90813 Vulnerability Analysis & Exploit Details

CVE-2026-90813 Vulnerability Summary

CVE-2026-90813: A vulnerability was detected in cosmicstack-labs mercury-agent up to 1.1.13. Affected is the function checkShellCommand of the file src/capabilities/permissions.ts of the component Shell Command Execution. The manipulation results in incorrect behavior order: validate before canonicalize. The attack may be launched remotely. The exploit is now public and may be used. The project was informed of the problem early through an issue report but has not responded yet.

CVE-2026-90813 References

External References

• https://github.com/cosmicstack-labs/mercury-agent/
• https://github.com/cosmicstack-labs/mercury-agent/issues/95
• https://vuldb.com/cve/CVE-2026-90813
• https://vuldb.com/submit/922879
• https://vuldb.com/vuln/403315
• https://vuldb.com/vuln/403315/cti

CWE Common Weakness Enumeration

CAPEC Common Attack Pattern Enumeration and Classification

• Leverage Alternate Encoding CAPEC-267 An adversary leverages the possibility to encode potentially harmful input or content used by applications such that the applications are ineffective at validating this encoding standard.
• Using Leading 'Ghost' Character Sequences to Bypass Input Filters CAPEC-3 Some APIs will strip certain leading characters from a string of parameters. An adversary can intentionally introduce leading "ghost" characters (extra characters that don't affect the validity of the request at the API layer) that enable the input to pass the filters and therefore process the adversary's input. This occurs when the targeted API will accept input data in several syntactic forms and interpret it in the equivalent semantic way, while the filter does not take into account the full spectrum of the syntactic forms acceptable to the targeted API.
• Using Unicode Encoding to Bypass Validation Logic CAPEC-71 An attacker may provide a Unicode string to a system component that is not Unicode aware and use that to circumvent the filter or cause the classifying mechanism to fail to properly understanding the request. That may allow the attacker to slip malicious data past the content filter and/or possibly cause the application to route the request incorrectly.
• Using Escaped Slashes in Alternate Encoding CAPEC-78 This attack targets the use of the backslash in alternate encoding. An adversary can provide a backslash as a leading character and causes a parser to believe that the next character is special. This is called an escape. By using that trick, the adversary tries to exploit alternate ways to encode the same character which leads to filter problems and opens avenues to attack.
• Using Slashes in Alternate Encoding CAPEC-79 This attack targets the encoding of the Slash characters. An adversary would try to exploit common filtering problems related to the use of the slashes characters to gain access to resources on the target host. Directory-driven systems, such as file systems and databases, typically use the slash character to indicate traversal between directories or other container components. For murky historical reasons, PCs (and, as a result, Microsoft OSs) choose to use a backslash, whereas the UNIX world typically makes use of the forward slash. The schizophrenic result is that many MS-based systems are required to understand both forms of the slash. This gives the adversary many opportunities to discover and abuse a number of common filtering problems. The goal of this pattern is to discover server software that only applies filters to one version, but not the other.
• Using UTF-8 Encoding to Bypass Validation Logic CAPEC-80 This attack is a specific variation on leveraging alternate encodings to bypass validation logic. This attack leverages the possibility to encode potentially harmful input in UTF-8 and submit it to applications not expecting or effective at validating this encoding standard making input filtering difficult. UTF-8 (8-bit UCS/Unicode Transformation Format) is a variable-length character encoding for Unicode. Legal UTF-8 characters are one to four bytes long. However, early version of the UTF-8 specification got some entries wrong (in some cases it permitted overlong characters). UTF-8 encoders are supposed to use the "shortest possible" encoding, but naive decoders may accept encodings that are longer than necessary. According to the RFC 3629, a particularly subtle form of this attack can be carried out against a parser which performs security-critical validity checks against the UTF-8 encoded form of its input, but interprets certain illegal octet sequences as characters.

Other 5 Recently Published CVEs Vulnerabilities

• CVE-2026-90896 – Missing Authentication for Critical Function (CWE-306) in the checkout session lookup handler (src/app/api/stripe/checkout_sessions/route.ts), expo...
• CVE-2026-90824 – A vulnerability has been found in GPAC 26.07.0. Affected is the function gf_sg_dom_event_bubble of the file src/scenegraph/dom_events.c of the comp...
• CVE-2026-90820 – A security vulnerability has been detected in a2aproject a2a-java 1.2.0. The impacted element is the function AuthorizationRequestHandlerDecorator....
• CVE-2026-90819 – A weakness has been identified in a2aproject a2a-java 1.2.0. The affected element is the function BasePushNotificationSender.dispatchNotification o...
• CVE-2026-90818 – A security flaw has been discovered in netease-youdao LobsterAI 2026.6.15/2026.8.28/2026.9.3/2026.9.4. Impacted is the function OpenClawConfigSync....