GHSA-8823-QG2X-PV9F is a high-severity uncontrolled resource consumption vulnerability in ultimate-sitemap-parser (pip), affecting versions <= 1.8.0. It is fixed in 1.8.1.
Gzip Decompression Bomb Bypasses Sitemap Size Limit Summary ultimate-sitemap-parser enforces a 100 MiB size limit on sitemap responses, but applies it only to the compressed bytes received over the network. When a .gz sitemap is fetched, usp/helpers.py:239 calls gziplib.decompress(data) with no output-size cap, allowing an attacker-controlled server to serve a small gzip-compressed payload (~549 KB) that expands to over 120 MiB in process memory. This completely bypasses the declared limit and can exhaust memory or crash any process that calls sitemaptreeforhomepage() against an untrusted site. Details The library declares a maximum sitemap size constant in usp/fetchparse.py:64: Despite the comment saying "uncompressed", this value is passed directly to the HTTP client layer at usp/fetchparse.py:130: The HTTP client (usp/webclient/requestsclient.py:57-58) slices only the raw compressed response bytes: The truncated (but still compressed) bytes are then passed through the pipeline to usp/fetchparse.py:175: Inside ungzippedresponsecontent (usp/helpers.py:265-267), when the URL ends in .gz or the response carries a gzip content type, decompression is triggered: The gunzip function (usp/helpers.py:239) decompresses without any output-size guard: No post-decompression size check exists anywhere in the call chain. Dynamic reproduction confirmed that 549,213 bytes of compressed input passed the 100 MiB gate check (compressed < limit → True) and then expanded to 125,829,234 bytes (120.0 MiB) in memory with no exception raised. PoC Environment setup: Alternatively, run directly: PoC script (poc.py), abbreviated attack flow: Expected output: The parser fetches /sitemap.xml.gz, passes the compressed-size gate check, decompresses 549 KB into 120 MiB in process memory, and returns normally without raising an exception. Remediation: Impact Any application that calls sitemaptreeforhomepage() (or the underlying fetch/parse pipeline) against an attacker-controlled or compromised domain is vulnerable. The attacker only needs to control a web server that serves a valid robots.txt pointing to a gzip-compressed sitemap URL. No authentication or special configuration is required; the vulnerability is triggered by default library behavior. A ~549 KB compressed payload expands to 120 MiB in process memory. Larger bombs are possible up to the compressed-size limit (100 MiB of compressed data could expand to tens of gigabytes). Repeated requests or sufficiently large bombs can cause out-of-memory crashes, service disruptions, or denial of service in any process or service that performs sitemap crawling. This vulnerability is a Denial of Service via Uncontrolled Resource Consumption (Decompression Bomb / Zip Bomb). Affected parties include: SEO tooling, search engine crawlers, and indexing services using this library. Web frameworks and microservices that expose a sitemap-crawling endpoint to external input. Any automated pipeline that regularly crawls third-party sitemaps. Reproduction artifacts Dockerfile poc.py
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
GHSA-8823-QG2X-PV9F has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (1.8.1). Upgrading removes the vulnerable code path.
pip
ultimate-sitemap-parser (<= 1.8.0)ultimate-sitemap-parser → 1.8.1 (pip)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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GHSA-8823-QG2X-PV9F is a high-severity uncontrolled resource consumption vulnerability in ultimate-sitemap-parser (pip), affecting versions <= 1.8.0. It is fixed in 1.8.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
GHSA-8823-QG2X-PV9F has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
ultimate-sitemap-parser (pip) versions <= 1.8.0 is affected.
Yes. GHSA-8823-QG2X-PV9F is fixed in 1.8.1. Upgrade to this version or later.
Whether GHSA-8823-QG2X-PV9F is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade ultimate-sitemap-parser to 1.8.1 or later.