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TI-2026-40146 Aliases CVE-2026-55617GHSA-94jp-7776-qj6q

Hydro: Insufficient session expiration when recreating sessions

Priority LOW 31CWE-613Published · Updated

Key facts

Attack vector
Network
Privileges required
High
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Security bypass
Confidentiality · integrity · availability
High · None · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-613.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00473 41st percentileScored 2026-11-07
Fix Fixed Hydro (hydro-dev): 5.0.2hydrooj (npm): 5.0.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
hydro-devHydro4.10.4 to before 5.0.25.0.2Patch availableCNA
—hydrooj (npm)4.10.4 to before 5.0.25.0.2Patch availableGHSA-94jp-7776-qj6q
  • Hydro Vendorhydro-dev Affected 4.10.4 to before 5.0.2 Fixed in 5.0.2 Patch available CNA
  • hydrooj (npm) Vendor— Affected 4.10.4 to before 5.0.2 Fixed in 5.0.2 Patch available GHSA-94jp-7776-qj6q

Remediation

  • Fix · CNA Hydro (hydro-dev) Fixed in 5.0.2
  • Fix · GHSA-94jp-7776-qj6q hydrooj (npm) Fixed in 5.0.2 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-55617
  2. 2026-10-03 Alias added: GHSA-94jp-7776-qj6q

References

Sources