CVE-2026-44432 urllib3: Decompression-bomb safeguards bypassed in parts of the streaming API
Attackers can cause excessive resource consumption and denial of service in applications using urllib3 by exploiting decompression-bomb safeguards bypasses.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-44432?
CVE-2026-44432 is a high-severity denial of service vulnerability in urllib3, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
urllib3 is an HTTP client library for Python. From 2.6.0 to before 2.7.0, urllib3 could decompress the whole response instead of the requested portion (1) during the second HTTPResponse.read(amt=N) call when the response was decompressed using the official Brotli library or (2) when HTTPResponse.drain_conn() was called after the response had been read and decompressed partially (compression algorithm did not matter here). These issues could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This could result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data) on the client side. This vulnerability is fixed in 2.7.0.
Weakness: CWE-409
Which versions are affected by CVE-2026-44432?
3 open source packages ship an affected version, including urllib3. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
urllib3 PyPI | From 2.6.0 | 2.7.0 |
urllib3 PyPI | From 2.6.0 | 2.7.0 |
urllib3 PyPI | From 2.6.0 | 2.7.0 |
Linux distribution packages (27)
python-cryptography Red Hat:hummingbird:1 | All versions | 0:48.0.0-3.hum1 |
python-rpds-py Red Hat:hummingbird:1 | All versions | 0:2026.5.1-1.hum1 |
python-sentry-sdk Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python-trustme Red Hat:hummingbird:1 | All versions | 0:1.2.1-2.hum1 |
python-trustme-doc Red Hat:hummingbird:1 | All versions | 0:1.2.1-2.hum1 |
python3-cryptography Red Hat:hummingbird:1 | All versions | 0:48.0.0-3.hum1 |
python3-rpds-py Red Hat:hummingbird:1 | All versions | 0:2026.5.1-1.hum1 |
python3-sentry-sdk Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+aiohttp Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+asyncpg Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+bottle Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+celery Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+django Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+falcon Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+fastapi Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+flask Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+grpcio Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+http2 Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+httpx Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+pure_eval Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+pymongo Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+rq Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+sqlalchemy Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+starlette Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-sentry-sdk+tornado Red Hat:hummingbird:1 | All versions | 0:2.48.0-4.1.hum1 |
python3-trustme Red Hat:hummingbird:1 | All versions | 0:1.2.1-2.hum1 |
python-urllib3 openSUSE:Tumbleweed | All versions | 2.7.0-1.1 |
Products include Python Urllib3.
How do I fix CVE-2026-44432?
Upgrade urllib3 to 2.7.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-44432 being exploited?
There is no known exploitation of CVE-2026-44432 in the wild and no public exploit code.
Other vulnerabilities in urllib3
- CVE-2026-97689 urllib3: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory
- CVE-2026-21441 urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API)
- CVE-2025-66418 urllib3 allows an unbounded number of links in the decompression chain
- CVE-2025-66471 urllib3 Streaming API improperly handles highly compressed data
- CVE-2026-44431 urllib3: Sensitive headers forwarded across origins in proxied low-level redirects
Sources
Also known as BELL-CVE-2026-44432, CLEANSTART-2026-UR98453, CLEANSTART-2026-WH98389, DEBIAN-CVE-2026-44432, ECHO-61da-f889-9d2c, GHSA-mf9v-mfxr-j63j and 31 more.