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CVE-2026-59939 describes a denial-of-service (DoS) vulnerability in the Python `httplib2` HTTP client library, affecting all versions prior to 0.32.0. The flaw resides in the `_decompressContent` function inside httplib2/__init__.py, which handles HTTP responses with `Content-Encoding: gzip` or deflate. The library automatically decompresses such bodies, but does so without imposing any limit on the size of the decompressed output. A malicious or compromised HTTP server can exploit this by sending a small compressed payload—often referred to as a “decompression bomb”—that expands to an arbitrarily large amount of data in memory. Because the decompression is unbounded, the client process may exhaust available RAM, leading to a `MemoryError` exception or triggering the operating system’s Out‑Of‑Memory (OOM) killer, which terminates the process. This creates an asymmetric resource consumption scenario: the attacker expends minimal network bandwidth while the victim’s memory is overwhelmed.
The vulnerability is rooted in the absence of input validation and resource limiting during decompression. The library’s design assumes that decompressed content will stay within reasonable bounds, but this assumption fails when confronted with specially crafted compressed data. An attacker can generate a compressed response that inflates to gigabytes or even terabytes, while the original network transmission remains tiny. The impact is not limited to a simple crash—it can cause complete application failure and system instability, especially in environments where `httplib2` is used for automated data processing or in server-side applications where resource exhaustion could affect service availability. The issue is classified under CWE‑400 (Uncontrolled Resource Consumption). Exploitation requires minimal skill; the attacker only needs control over an HTTP server that can return maliciously compressed content. The fix in version 0.32.0 introduces bounded decompression with a hard output limit, a safe‑size threshold, and an output‑to‑input ratio check, raising an error when any of these limits are exceeded. Organizations are urged to upgrade immediately or implement network‑level mitigations such as proxy‑enforced response size limits.
DailyCVE Form:
Platform: Python
Version: 0.7.0–0.31.2
Vulnerability: Unbounded decompression bomb
Severity: Low
date: 2026‑07‑08
Prediction: Patch 2026‑06‑26
What Undercode Say:
Analytics from threat intelligence sources indicate that while the CVE has a low severity rating, the widespread use of `httplib2` in legacy and production systems makes it a prime target for denial‑of‑service attacks. Automated scanners and security advisories (e.g., AIKIDO‑2026‑721881) have already flagged vulnerable versions, and proof‑of‑concept exploits are expected to surface quickly. The attack requires no authentication and can be launched from any malicious server that the client contacts, making it particularly dangerous for applications that fetch data from untrusted or third‑party APIs. Monitoring memory usage and response sizes is recommended to detect potential exploitation attempts.
Check installed httplib2 version pip show httplib2 | grep Version List all vulnerable versions (0.7.0 through 0.31.2) pip list --outdated | grep httplib2 Upgrade to patched version pip install --upgrade httplib2==0.32.0
Exploit:
An attacker sets up an HTTP server that responds to any request with a `Content-Encoding: gzip` header and a small gzip‑compressed payload designed to expand massively (e.g., a 10 KB compressed file that decompresses to 10 GB). When a vulnerable `httplib2` client sends a request to this server, the library automatically decompresses the response without limits, causing memory exhaustion. The following Python snippet simulates the vulnerable behavior (for educational purposes only):
import httplib2
h = httplib2.Http()
Point to a malicious server serving a decompression bomb
resp, content = h.request("http://malicious-server/bomb", "GET")
At this point, memory may be exhausted
Protection:
- Upgrade to `httplib2` version 0.32.0 or later, which includes bounded decompression with size and ratio limits.
- Apply network‑level controls such as a reverse proxy or API gateway that enforces a maximum response size (e.g., `nginx`
client_max_body_sizeorproxy_buffer_size). - Implement application‑level validation by checking the `Content-Encoding` header and manually limiting the size of decompressed data before processing.
- Monitor memory usage and set alerts for unusual spikes in client processes that use
httplib2.
Impact:
- Denial of Service: Successful exploitation causes the client process to crash due to `MemoryError` or OOM‑kill, disrupting application availability.
- Resource Exhaustion: The attack consumes excessive RAM, potentially affecting other processes on the same host and leading to system‑wide instability.
- Operational Disruption: Applications that rely on `httplib2` for critical integrations (e.g., cloud APIs, payment gateways) may experience prolonged downtime until the process is restarted.
- No Data Breach: The vulnerability does not allow data exfiltration or code execution; it is purely a resource‑consumption DoS.
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Sources:
Reported By: nvd.nist.gov
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