CVE-2026-55617

MEDIUMPre-NVD 6.96.9
EchelonGraph scoreLOW confidence

This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). 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: secondary
Trending — 3 sources updated this week
6.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.9Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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
6.9(low)
EG Risk
31(Track)
EG Risk 31/100SSVC: Track

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%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
20%
KEV
Not listed

Published

June 18, 2026

Last Modified

September 15, 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
github Patch Available

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 rangeFixed inDependents
hydrooj—5.0.2—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 8× 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. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-17 19:31 UTCEPSS rescore
  3. 2026-09-16 14:08 UTCEPSS rescore
  4. 2026-09-15 19:41 UTCEG score recompute
  5. 2026-09-15 18:25 UTCEG score recompute
  6. 2026-09-15 15:35 UTCEG score recompute
  7. 2026-09-15 14:53 UTCEG score recompute▲ 6.90
  8. 2026-09-15 14:52 UTCMITRE cvelistV5CVSS v3 → 6.9 · CVSS v4 → 6.9
  9. 2026-08-02 03:50 UTCEG score recompute
  10. 2026-07-26 18:48 UTCEG score recompute
  11. 2026-07-23 03:20 UTCEG score recompute
  12. 2026-06-18 13:45 UTCEG score recompute

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 in the National Vulnerability Database on June 18, 2026, with the most recent update on September 15, 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% probability of exploitation in the next 30 days, which ranks it in the top 80.2% of all scored CVEs.
What is the CVSS score of CVE-2026-55617?
CVE-2026-55617 has a CVSS v3 base score of 6.9 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-55617?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55617, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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