Hydro: Insufficient session expiration when recreating sessions (CVE-2026-55617) | HOL Guard CVE

Medium severityCVE-2026-55617GHSA-94JP-7776-QJ6Q

Hydro: Insufficient session expiration when recreating sessions

Answer in brief

CVE-2026-55617 records a Medium severity vulnerability in Hydro: Insufficient session expiration when recreating sessions. The current sources do not mark it as known exploited. The current feed maps hydro-dev/Hydro (generic), hydrooj (npm). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 15, 2026Updated Sep 15, 2026Source checked Sep 17, 2026First seen by HOL Jun 19, 2026Material review Sep 15, 2026

Upstream Advisory

Key facts

Risk: Medium
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps hydro-dev/Hydro (generic), hydrooj (npm). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
hydro-dev/Hydrogeneric	>= 4.10.4, < 5.0.2	Not reported
hydroojnpm	>=4.10.4,<=5.0.1	5.0.2

Recommended response

Check inventory. Check lockfiles and deployed manifests for hydro-dev/Hydro, hydrooj.
Review the reported fix. Update hydrooj to 5.0.2 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jun 19, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.