dnspython has excessive memory and CPU use

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

• CVE-2026-128089: 0.53% estimated exploitation activity in the next 30 days; percentile 45.21 (FIRST EPSS, 2026-11-14). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A maliciously crafted zone file could use a WKS record to consume excessive memory and CPU, possibly causing the process to exit due to memory exhaustion.

Details The `from_text()` parser does not check that a WKS record service number is between 0 and 65535 inclusive. It then uses this number to resize the bitmap to accommodate a bit with that offset. This can cause extremely large memory allocations, and also extends the array very inefficiently, wasting CPU.

Proof of concept This demonstrates the failure to limit the service number, though with a value that does not cause excessive memory or CPU consumption. ``` rd = dns.rdata.from_text("IN", "WKS", "10.0.0.1 udp 65536") ```

Impact If dnspython is used to read zonefile format where the attacker can control the type and rdata text, the program may consume excessive memory or CPU, denying service.

Published by the source

13 Nov 2026, 20:19 UTC

Last modified by the source

13 Nov 2026, 20:30 UTC

Source last checked

14 Nov 2026, 07:50 UTC

1. Revision 2 · amended · 14 Nov 2026

   Amended from osv record GHSA-vvf4-9x63-8xvv

2. Revision 1 · created · 13 Nov 2026

   Published from ghsa record GHSA-vvf4-9x63-8xvv

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# Patch Next advisory brief: CVE-2026-128089

Advisory: dnspython has excessive memory and CPU use
IDs: CVE-2026-128089, GHSA-vvf4-9x63-8xvv
Record: https://patchnext.com/advisories/cve-2026-128089 (revision 2, source checked 14 Nov 2026, 07:50 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: dnspython 2.9.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI dnspython: affected < 2.9.2; fixed in 2.9.2

## Suggested inspection (read-only)
- `python -m pip show dnspython`: 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 dnspython.
- 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://github.com/advisories/GHSA-vvf4-9x63-8xvv (GitHub-reviewed advisory GHSA-vvf4-9x63-8xvv lists affected ranges: PyPI dnspython >=0 <2.9.2)
- Verified: https://osv.dev/vulnerability/GHSA-vvf4-9x63-8xvv (OSV record GHSA-vvf4-9x63-8xvv lists affected ranges: PyPI dnspython >=0 <2.9.2 (fixed))

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