CVE-2026-55617

MEDIUMPre-NVD 6.96.9
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (40th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Trending — 4 sources updated this week

Also known asEUVD-2026-78768 (ENISA EUVD) · GHSA-94jp-7776-qj6q (GitHub Security Advisories)Source: ENISA EUVD

6.9EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • 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 31/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity69% × 45%
Impact severity (EG Severity): CVSS 6.9 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.5% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
40th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (6.9): severity, escalated by confirmed exploitation. This CVE's 6.9 is its impact severity (EG Severity), not escalated.

EG Severity
6.9 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
EG Likelihood
0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track 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). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

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 pull request

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 advisoryMentions 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.

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
npmhydrooj @ 5.0.2 (fixes >= 4.10.4, <= 5.0.1)—ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

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 10× in last 7d / 40× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-11-02 16:45 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  2. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  3. 2026-11-01 07:43 UTCGHSA enrichmentGHSA-94jp-7776-qj6q · GitHub severity MODERATE
  4. 2026-11-01 07:43 UTCEG score recompute
  5. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  6. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  7. 2026-10-30 10:55 UTCOSV refresh
  8. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  9. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  10. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  11. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  12. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  13. 2026-10-25 14:18 UTCEG score recompute
  14. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  15. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  16. 2026-10-22 21:14 UTCEG score recompute
  17. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  18. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  19. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  20. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  21. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  22. 2026-10-18 03:30 UTCEG score recompute
  23. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  24. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  25. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
Show 39 more
  1. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  2. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  3. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  4. 2026-10-12 15:55 UTCEG score recompute
  5. 2026-10-11 19:38 UTCEG score recompute
  6. 2026-10-11 16:54 UTCEG score recompute
  7. 2026-10-11 14:17 UTCEG score recompute
  8. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  9. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  10. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  11. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  12. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  13. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  14. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  15. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  16. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  17. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  18. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  19. 2026-09-30 18:12 UTCEG score recompute
  20. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  21. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  22. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  23. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  24. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  25. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  26. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  27. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  28. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  29. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  30. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  31. 2026-09-15 19:41 UTCEG score recompute
  32. 2026-09-15 18:25 UTCEG score recompute
  33. 2026-09-15 15:35 UTCEG score recompute
  34. 2026-09-15 14:53 UTCEG score recomputeFirst assessed: 6.9 MEDIUM
  35. 2026-09-15 14:52 UTCMITRE cvelistV5CVSS v3 → 6.9 · CVSS v4 → 6.9
  36. 2026-08-02 03:50 UTCEG score recompute
  37. 2026-07-26 18:48 UTCEG score recompute
  38. 2026-07-23 03:20 UTCEG score recompute
  39. 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-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-55617 published?
The CVE record for CVE-2026-55617 was published on June 18, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 30, 2026; the record at its source may have been updated since.
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 (40th 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-55617

Explore →

Is Your Infrastructure Affected by CVE-2026-55617?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Book a Demo →Browse All CVEs