hydro-dev Hydro up to 5.0.1 Session Recreation Logic base.ts authentication replay

Summaryinfo

A vulnerability, which was classified as critical, has been found in hydro-dev Hydro up to 5.0.1. Affected by this issue is some unknown functionality of the file packages/hydrooj/src/service/layers/base.ts of the component Session Recreation Logic. This manipulation causes authentication replay. This vulnerability is handled as CVE-2026-55617. The attack can be initiated remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in hydro-dev Hydro up to 5.0.1. It has been declared as critical. Affected by this vulnerability is an unknown functionality of the file packages/hydrooj/src/service/layers/base.ts of the component Session Recreation Logic. The manipulation with an unknown input leads to a authentication replay vulnerability. The CWE definition for the vulnerability is CWE-294. A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Hydro is a next-generation high-performance online judge platform. From 4.10.4 until 5.0.2, the session recreation logic in packages/hydrooj/src/service/layers/base.ts creates a replacement session token without deleting the previous token from the server-side session token store, so an old sid cookie can remain valid after logout or another renewal flow. An attacker who possesses a victim's previously valid stale cookie can replay it over HTTP or HTTPS without knowing the victim's username or password and without victim interaction at exploitation time. Successful replay can take over the victim's account, disclose private data, and permit unauthorized modification or deletion of data available to that account. This issue is fixed in version 5.0.2.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-55617 since 06/17/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1040 according to MITRE ATT&CK.

Upgrading to version 5.0.2 eliminates this vulnerability.

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Productinfo

Vendor

• hydro-dev

Name

• Hydro

Version

• 5.0.0
• 5.0.1

Website

• Product: https://github.com/hydro-dev/Hydro/

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