CVE-2026-55617

MEDIUMPre-NVD 6.96.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (38th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
6.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 6.9Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
6.9
EG Score
6.9MEDIUMmedium confidence
EG Risk
31
EG Risk 31/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity69% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
39th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

June 18, 2026

Last Modified

September 30, 2026

Advisory Details (4)

Auto-updated Sep 15, 2026
Patch available. Sources: github, github_pr, github_commit.
github_commit

commit 8d76be8f0b83 (hydro-dev/Hydro)

Fix landed in hydro-dev/Hydro commit 8d76be8f0b83 — awaiting tagged release

https://github.com/hydro-dev/Hydro/commit/8d76be8f0b83d911bf7671962b0467e9d4b5719a
github_commit

commit 8450390fcce5 (hydro-dev/Hydro)

Fix landed in hydro-dev/Hydro commit 8450390fcce5 — awaiting tagged release

https://github.com/hydro-dev/Hydro/commit/8450390fcce5f7dc3f11c43a14f1d76dbb949a0d
github_pr

core: delete old session after recreate

Fix merged in hydro-dev/Hydro PR #1173 on 2026-06-06 — awaiting tagged release

https://github.com/hydro-dev/Hydro/pull/1173
githubMentions a patch (unverified)

Insufficient session expiration when recreating sessions in Hydro · Advisory · hydro-dev/Hydro · GitHub

https://github.com/hydro-dev/Hydro/security/advisories/GHSA-94jp-7776-qj6q

Vendor Advisories for CVE-2026-55617(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFix by version rangeDependents
hydrooj—
  • 4.10.4 up to 5.0.2: fixed in 5.0.2
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 27× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-10 20:00 UTCEPSS rescore
  2. 2026-10-09 20:07 UTCEPSS rescore
  3. 2026-10-08 17:12 UTCEPSS rescore
  4. 2026-10-07 23:48 UTCEPSS rescore
  5. 2026-10-06 15:18 UTCEPSS rescore
  6. 2026-10-05 17:43 UTCEPSS rescore
  7. 2026-10-04 23:22 UTCEPSS rescore
  8. 2026-10-03 14:26 UTCEPSS rescore
  9. 2026-10-02 17:56 UTCEPSS rescore
  10. 2026-10-01 19:50 UTCEPSS rescore
  11. 2026-09-30 18:12 UTCEG score recompute
  12. 2026-09-30 15:03 UTCEPSS rescore
  13. 2026-09-29 15:22 UTCEPSS rescore
  14. 2026-09-28 13:51 UTCEPSS rescore
  15. 2026-09-27 13:48 UTCEPSS rescore
  16. 2026-09-26 15:59 UTCEPSS rescore
  17. 2026-09-24 14:04 UTCEPSS rescore
  18. 2026-09-23 17:54 UTCEPSS rescore
  19. 2026-09-20 20:16 UTCEPSS rescore
  20. 2026-09-18 19:28 UTCEPSS rescore
  21. 2026-09-17 19:31 UTCEPSS rescore
  22. 2026-09-16 14:08 UTCEPSS rescore
  23. 2026-09-15 19:41 UTCEG score recompute
  24. 2026-09-15 18:25 UTCEG score recompute
  25. 2026-09-15 15:35 UTCEG score recompute
Show 6 more
  1. 2026-09-15 14:53 UTCEG score recompute▲ 6.90
  2. 2026-09-15 14:52 UTCMITRE cvelistV5CVSS v3 → 6.9 · CVSS v4 → 6.9
  3. 2026-08-02 03:50 UTCEG score recompute
  4. 2026-07-26 18:48 UTCEG score recompute
  5. 2026-07-23 03:20 UTCEG score recompute
  6. 2026-06-18 13:45 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55617?
CVE-2026-55617 is a medium vulnerability published on June 18, 2026. 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…
When was CVE-2026-55617 disclosed?
CVE-2026-55617 was first published on June 18, 2026, with the most recent update on September 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55617 actively exploited?
CVE-2026-55617 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (39th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55617?
CVE-2026-55617 has a CVSS base score of 6.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55617?
A fix for CVE-2026-55617 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55617 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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