FKIE_CVE-2026-54742

Vulnerability from fkie_nvd - Published: 2026-08-19 20:17 - Updated: 2026-08-20 20:17
Severity
5.1 (Medium) - CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Summary
Lemmy is a link aggregator and forum for the fediverse. From 0.19.18 until 0.19.19 and 1.0.0-alpha.20, a community moderator can feature or unfeature posts in other communities through federated CollectionAdd and CollectionRemove activities using CollectionType::Featured. After verify_mod_action authorizes the actor against self.community(), the receive handlers in crates/apub/activities/src/community/collection_add.rs and crates/apub/activities/src/community/collection_remove.rs dereference self.object as an ApubPost and update featured_community without verifying that post.community_id equals community.id. A moderator can therefore target an unrelated post owned by another community, push it into featured feeds and listings, or undo another community's legitimate curation decision. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.20.
References
security-advisories@github.comhttps://github.com/LemmyNet/lemmy/commit/108d78c592cc88bac2b0bf52ca6631be54f6fb23
security-advisories@github.comhttps://github.com/LemmyNet/lemmy/commit/abe256243822526dcd4bca857f7c0adeb49944f5
security-advisories@github.comhttps://github.com/LemmyNet/lemmy/pull/6500
security-advisories@github.comhttps://github.com/LemmyNet/lemmy/pull/6501
security-advisories@github.comhttps://github.com/LemmyNet/lemmy/releases/tag/0.19.19
security-advisories@github.comhttps://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.20
security-advisories@github.comhttps://github.com/LemmyNet/lemmy/security/advisories/GHSA-gwfj-h8r7-792v
security-advisories@github.comhttps://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19
134c704f-9b21-4f2e-91b3-4a467353bcc0https://github.com/LemmyNet/lemmy/security/advisories/GHSA-gwfj-h8r7-792v
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "lemmy",
          "vendor": "LemmyNet",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.19.19"
            },
            {
              "status": "affected",
              "version": "\u003e= 1.0.0-alpha.0, \u003c 1.0.0-alpha.20"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Lemmy is a link aggregator and forum for the fediverse. From 0.19.18 until 0.19.19 and 1.0.0-alpha.20, a community moderator can feature or unfeature posts in other communities through federated CollectionAdd and CollectionRemove activities using CollectionType::Featured. After verify_mod_action authorizes the actor against self.community(), the receive handlers in crates/apub/activities/src/community/collection_add.rs and crates/apub/activities/src/community/collection_remove.rs dereference self.object as an ApubPost and update featured_community without verifying that post.community_id equals community.id. A moderator can therefore target an unrelated post owned by another community, push it into featured feeds and listings, or undo another community\u0027s legitimate curation decision. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.20."
    }
  ],
  "id": "CVE-2026-54742",
  "lastModified": "2026-08-20T20:17:35.410",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 5.1,
          "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",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "HIGH",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:L/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",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "LOW",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-54742",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-20T20:01:14.417876Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-19T20:17:17.093",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/LemmyNet/lemmy/commit/108d78c592cc88bac2b0bf52ca6631be54f6fb23"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/LemmyNet/lemmy/commit/abe256243822526dcd4bca857f7c0adeb49944f5"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/LemmyNet/lemmy/pull/6500"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/LemmyNet/lemmy/pull/6501"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.19"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.20"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-gwfj-h8r7-792v"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-gwfj-h8r7-792v"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-863"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}



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  • 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.
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