CVE-2026-71557: go-git Malicious Reference Names May Modify Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-qgq7-7hm3-q39j",
  "modified" : "2026-08-07T16:41:51Z",
  "published" : "2026-08-07T16:41:51Z",
  "aliases" : [ "CVE-2026-71557" ],
  "summary" : "go-git: Malicious reference names may modify files outside the reference storage",
  "details" : "### Impact\nA path traversal issue in `go-git` could allow malicious reference names to access files outside the repository's intended reference storage.\n\nLoose references are stored under `.git/<reference-name>`. The reference name was previously used as a path without verifying that the resolved path remained within the reference storage. A name such as `refs/heads/../../config` could therefore resolve to unrelated repository metadata such as `.git/config` or `.git/HEAD`.\n\nA malicious Git server could advertise such a reference name. The name may also survive refspec mapping; for example, it could be mapped to `refs/remotes/origin/../../config` during a clone or fetch operation.\n\nThis vulnerability affects filesystem-backed repositories using the `storage/filesystem` package and its `dotgit` reference storage. Users relying exclusively on the in-memory storage implementation, `storage/memory`, are not affected, because reference names are not resolved as filesystem paths.\n\nExploitation requires an application using `go-git` with filesystem-backed storage to interact with a malicious Git server or otherwise process attacker-controlled reference names.\n\n### Patches\nThe issue has been addressed by validating reference names at the `dotgit` storage entry points and rejecting names whose resolved paths could escape the reference storage.\n\nUsers of filesystem-backed storage should upgrade to a patched version.\n\n### Workarounds\nApplications that exclusively use `storage/memory` are not affected and do not require a workaround for this vulnerability.\n\nFor applications using filesystem-backed storage, avoid cloning from or fetching from untrusted Git servers until an upgrade is possible.\n\nApplications that directly construct or process reference names may also validate them before passing them to filesystem-backed `go-git` storage. Application-level validation should only be considered a temporary mitigation and does not replace upgrading to a patched version.\n\n### References\n- Fixes:\n  - https://github.com/go-git/go-git/pull/2247\n  - https://github.com/go-git/go-git/pull/2254\n\n### Credits\n\nThanks to @Saku0512 for reporting this issue and @Sahana2524 for proposing the initial fix. 🙇",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/go-git/go-git/v5"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.19.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.19.1"
    }
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/go-git/go-git/v6"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.0.0-alpha.5"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.0.0-alpha.4"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/go-git/go-git/security/advisories/GHSA-qgq7-7hm3-q39j"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-git/go-git/pull/2247"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-git/go-git/pull/2254"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-git/go-git/commit/4a0e66d555de5f9a30c31e2df64f445f42bd01e7"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-git/go-git/commit/da9f7d8a0e98b475600177348d6ece384a370f36"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/go-git/go-git"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-git/go-git/releases/tag/v5.19.2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-git/go-git/releases/tag/v6.0.0-alpha.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-07T16:41:51Z",
    "nvd_published_at" : null
  }
}