Vulnerability-Lookup

CVE-2026-55617 (GCVE-0-2026-55617)

Vulnerability from cvelistv5 – Published: 2026-09-15 14:45 – Updated: 2026-09-15 18:02

Title

Hydro: Insufficient session expiration when recreating sessions

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.

Severity

6.9 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-15 17:38 UTC

CWE

CWE-613 - Insufficient Session Expiration

Assigner

GitHub_M mitre root

References

4 references

URL	Tags
https://github.com/hydro-dev/Hydro/security/advis…	x_refsource_CONFIRM
https://github.com/hydro-dev/Hydro/pull/1173	x_refsource_MISC
https://github.com/hydro-dev/Hydro/commit/8450390…	x_refsource_MISC
https://github.com/hydro-dev/Hydro/commit/8d76be8…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
hydro-dev	Hydro	Affected: >= 4.10.4, < 5.0.2	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-55617

Vulnerability from fkie_nvd - Published: 2026-09-15 15:17 - Updated: 2026-09-15 19:17

Severity

6.9 (Medium) - CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/hydro-dev/Hydro/commit/8450390fcce5f7dc3f11c43a14f1d76dbb949a0d
	security-advisories@github.com	https://github.com/hydro-dev/Hydro/commit/8d76be8f0b83d911bf7671962b0467e9d4b5719a
	security-advisories@github.com	https://github.com/hydro-dev/Hydro/pull/1173
	security-advisories@github.com	https://github.com/hydro-dev/Hydro/security/advisories/GHSA-94jp-7776-qj6q

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "Hydro",
          "vendor": "hydro-dev",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 4.10.4, \u003c 5.0.2"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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\u0027s previously valid stale cookie can replay it over HTTP or HTTPS without knowing the victim\u0027s username or password and without victim interaction at exploitation time. Successful replay can take over the victim\u0027s 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."
    }
  ],
  "id": "CVE-2026-55617",
  "lastModified": "2026-09-15T19:17:22.433",
  "metrics": {
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      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
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          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.9,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
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          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
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    }
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  "vulnStatus": "Received",
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}

GHSA-94JP-7776-QJ6Q

Vulnerability from github – Published: 2026-06-18 13:06 – Updated: 2026-06-18 13:06

Summary

Hydro: Insufficient session expiration when recreating sessions

Details

Impact

Hydro contains an insufficient session expiration vulnerability in its session recreation logic. When a session is recreated, including during logout or other session renewal flows, Hydro creates a new session token but does not delete the previous server-side session token.

As a result, an old sid cookie may remain valid even after the legitimate user logs out or the session is recreated. An attacker who has obtained a victim's previous sid cookie can replay that cookie over HTTP or HTTPS and continue to access the affected Hydro instance as the victim.

The attacker does not need the victim's username or password. Exploitation requires possession of a previously valid stale sid cookie, but no user interaction is required at exploitation time.

Successful exploitation may allow account takeover within the affected Hydro instance. For a normal user account, this may allow disclosure of private data and unauthorized modification or deletion of data available to the victim.

Patches

The issue has been patched by deleting the old server-side session token before creating a new one during session recreation.

Patched in:

Pull request: https://github.com/hydro-dev/Hydro/pull/1173
Patch commit: https://github.com/hydro-dev/Hydro/commit/8450390fcce5f7dc3f11c43a14f1d76dbb949a0d
Merge commit: https://github.com/hydro-dev/Hydro/commit/8d76be8f0b83d911bf7671962b0467e9d4b5719a

Users should upgrade to a version containing this patch.

Workarounds

If upgrading immediately is not possible, administrators should reduce the risk by forcing all existing sessions to expire or by clearing the server-side session token store after applying a local patch.

Administrators should also review logs for suspicious use of stale sid cookies and rotate any exposed session cookies. However, these mitigations do not fully fix the vulnerability. The recommended remediation is to upgrade to a patched version.

Severity

6.9 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 5.0.1"
      },
      "package": {
        "ecosystem": "npm",
        "name": "hydrooj"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.10.4"
            },
            {
              "fixed": "5.0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55617"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-613"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-18T13:06:35Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nHydro contains an insufficient session expiration vulnerability in its session recreation logic. When a session is recreated, including during logout or other session renewal flows, Hydro creates a new session token but does not delete the previous server-side session token.\n\nAs a result, an old sid cookie may remain valid even after the legitimate user logs out or the session is recreated. An attacker who has obtained a victim\u0027s previous sid cookie can replay that cookie over HTTP or HTTPS and continue to access the affected Hydro instance as the victim.\n\nThe attacker does not need the victim\u0027s username or password. Exploitation requires possession of a previously valid stale sid cookie, but no user interaction is required at exploitation time.\n\nSuccessful exploitation may allow account takeover within the affected Hydro instance. For a normal user account, this may allow disclosure of private data and unauthorized modification or deletion of data available to the victim.\n\n### Patches\n\nThe issue has been patched by deleting the old server-side session token before creating a new one during session recreation.\n\nPatched in:\n\n- Pull request: https://github.com/hydro-dev/Hydro/pull/1173\n- Patch commit: https://github.com/hydro-dev/Hydro/commit/8450390fcce5f7dc3f11c43a14f1d76dbb949a0d\n- Merge commit: https://github.com/hydro-dev/Hydro/commit/8d76be8f0b83d911bf7671962b0467e9d4b5719a\n\nUsers should upgrade to a version containing this patch.\n\n### Workarounds\n\nIf upgrading immediately is not possible, administrators should reduce the risk by forcing all existing sessions to expire or by clearing the server-side session token store after applying a local patch.\n\nAdministrators should also review logs for suspicious use of stale sid cookies and rotate any exposed session cookies. However, these mitigations do not fully fix the vulnerability. The recommended remediation is to upgrade to a patched version.",
  "id": "GHSA-94jp-7776-qj6q",
  "modified": "2026-06-18T13:06:35Z",
  "published": "2026-06-18T13:06:35Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/hydro-dev/Hydro/security/advisories/GHSA-94jp-7776-qj6q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/hydro-dev/Hydro/pull/1173"
    },
    {
      "type": "WEB",
      "url": "https://github.com/hydro-dev/Hydro/commit/8450390fcce5f7dc3f11c43a14f1d76dbb949a0d"
    },
    {
      "type": "WEB",
      "url": "https://github.com/hydro-dev/Hydro/commit/8d76be8f0b83d911bf7671962b0467e9d4b5719a"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/hydro-dev/Hydro"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Hydro: Insufficient session expiration when recreating sessions"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-55617 (GCVE-0-2026-55617)

FKIE_CVE-2026-55617

GHSA-94JP-7776-QJ6Q

Impact

Patches

Workarounds

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Nomenclature

Related by attack behaviour