Ultimate Sitemap Parser (USP): Gzip Decompression Bomb Bypasses Sitemap Size Limit

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

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…

Published by the source

19 Jun 2026, 21:15 UTC

Last modified by the source

23 Jun 2026, 05:19 UTC

Source last checked

26 Oct 2026, 13:46 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-8823-qg2x-pv9f

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-8823-qg2x-pv9f

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# Patch Next advisory brief: GHSA-8823-qg2x-pv9f

Advisory: Ultimate Sitemap Parser (USP): Gzip Decompression Bomb Bypasses Sitemap Size Limit
IDs: GHSA-8823-qg2x-pv9f
Record: https://patchnext.com/advisories/ghsa-8823-qg2x-pv9f (revision 2, source checked 26 Oct 2026, 13:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ultimate-sitemap-parser 1.8.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI ultimate-sitemap-parser: affected <= 1.8.0; fixed in 1.8.1

## Suggested inspection (read-only)
- `python -m pip show ultimate-sitemap-parser`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ultimate-sitemap-parser.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-8823-qg2x-pv9f (OSV record GHSA-8823-qg2x-pv9f lists affected ranges: PyPI ultimate-sitemap-parser >=0 <1.8.1 (fixed))
- Verified: https://github.com/advisories/GHSA-8823-qg2x-pv9f (GitHub-reviewed advisory GHSA-8823-qg2x-pv9f lists affected ranges: PyPI ultimate-sitemap-parser >=0 <=1.8.0)

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