Vulnerability-Lookup

GHSA-6HV3-2R7G-774J

Vulnerability from github – Published: 2026-10-18 12:30 – Updated: 2026-10-18 12:30

Details

snac2 before 2.93 contains a heap-based buffer overflow vulnerability in _xs_json_load_lexer() that allows unauthenticated remote attackers to corrupt heap memory by sending JSON strings containing a \u0000 escape. Attackers can send a single crafted application/activity+json POST to activitypub_post_handler(), which parses it before signature checks, overflowing heap allocations and crashing the server.

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

8.7 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-112021"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-122"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-18T12:17:15Z",
    "severity": "HIGH"
  },
  "details": "snac2 before 2.93 contains a heap-based buffer overflow vulnerability in _xs_json_load_lexer() that allows unauthenticated remote attackers to corrupt heap memory by sending JSON strings containing a \\u0000 escape. Attackers can send a single crafted application/activity+json POST to activitypub_post_handler(), which parses it before signature checks, overflowing heap allocations and crashing the server.",
  "id": "GHSA-6hv3-2r7g-774j",
  "modified": "2026-10-18T12:30:29Z",
  "published": "2026-10-18T12:30:28Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-112021"
    },
    {
      "type": "WEB",
      "url": "https://codeberg.org/grunfink/snac2"
    },
    {
      "type": "WEB",
      "url": "https://codeberg.org/grunfink/snac2/commit/ec2c5c2046e0381bc942ec5d0d05ec861fe377e7"
    },
    {
      "type": "WEB",
      "url": "https://codeberg.org/grunfink/snac2/releases/tag/2.93"
    },
    {
      "type": "WEB",
      "url": "https://codeberg.org/grunfink/snac2/src/tag/2.92/xs_json.h#L283-L285"
    },
    {
      "type": "WEB",
      "url": "https://gist.github.com/nullenvk/2bf288e2d34cb3d4b7143e61dbf7d90b"
    },
    {
      "type": "WEB",
      "url": "https://nullenvk.pl/posts/02-snac2-json"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/snac2-before-2.93-heap-based-buffer-overflow-via-json-parser-xs-json-load-lexer"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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",
      "type": "CVSS_V4"
    }
  ]
}

CVE-2026-112021 (GCVE-0-2026-112021)

Vulnerability from cvelistv5 – Published: 2026-10-18 11:38 – Updated: 2026-10-19 16:05

Title

snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()

Summary

Severity

8.7 (High)


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

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-19 16:04 UTC

CWE

CWE-122 - Heap-based Buffer Overflow

Assigner

VulnCheck CNA under the mitre root

CNA scorecard B 84/100 over 6517 records in the last 180 days details

References

7 references

URL	Tags
https://nullenvk.pl/posts/02-snac2-json	technical-description
https://gist.github.com/nullenvk/2bf288e2d34cb3d4…	exploit
https://codeberg.org/grunfink/snac2/src/tag/2.92/…	technical-description
https://codeberg.org/grunfink/snac2/commit/ec2c5c…	patch
https://codeberg.org/grunfink/snac2/releases/tag/2.93	release-notes
https://codeberg.org/grunfink/snac2	product
https://www.vulncheck.com/advisories/snac2-before…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
grunfink	snac2	Affected: 0 , < 2.93 (custom)

Date Public

2026-07-08 00:00

Credits

nullenvk

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-112021",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-19T16:04:19.806894Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-19T16:05:15.544Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "snac2",
          "repo": "https://codeberg.org/grunfink/snac2",
          "vendor": "grunfink",
          "versions": [
            {
              "lessThan": "2.93",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "nullenvk"
        }
      ],
      "datePublic": "2026-07-08T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "snac2 before 2.93 contains a heap-based buffer overflow vulnerability in _xs_json_load_lexer() that allows unauthenticated remote attackers to corrupt heap memory by sending JSON strings containing a \\u0000 escape. Attackers can send a single crafted application/activity+json POST to activitypub_post_handler(), which parses it before signature checks, overflowing heap allocations and crashing the server."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.7,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          },
          "format": "CVSS"
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-122",
              "description": "Heap-based Buffer Overflow",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-18T11:38:40.652Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
      },
      "references": [
        {
          "tags": [
            "technical-description"
          ],
          "url": "https://nullenvk.pl/posts/02-snac2-json"
        },
        {
          "tags": [
            "exploit"
          ],
          "url": "https://gist.github.com/nullenvk/2bf288e2d34cb3d4b7143e61dbf7d90b"
        },
        {
          "tags": [
            "technical-description"
          ],
          "url": "https://codeberg.org/grunfink/snac2/src/tag/2.92/xs_json.h#L283-L285"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://codeberg.org/grunfink/snac2/commit/ec2c5c2046e0381bc942ec5d0d05ec861fe377e7"
        },
        {
          "tags": [
            "release-notes"
          ],
          "url": "https://codeberg.org/grunfink/snac2/releases/tag/2.93"
        },
        {
          "tags": [
            "product"
          ],
          "url": "https://codeberg.org/grunfink/snac2"
        },
        {
          "name": "VulnCheck Advisory: snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/snac2-before-2.93-heap-based-buffer-overflow-via-json-parser-xs-json-load-lexer"
        }
      ],
      "title": "snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()",
      "x_generator": {
        "engine": "vulncheck-endgame"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-112021",
    "datePublished": "2026-10-18T11:38:40.652Z",
    "dateReserved": "2026-10-18T01:24:56.329Z",
    "dateUpdated": "2026-10-19T16:05:15.544Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

Publication & reservation Sightings KEV catalogs Other timestamps

Loading timeline…

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