Twisted: DNS Response Spoofing in twisted.names Due to Missing Source Address Validation

Exploitation

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

CVSS

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

EPSS

• CVE-2026-83813: 0.11% estimated exploitation activity in the next 30 days; percentile 1.51 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary `twisted.names.dns.DNSDatagramProtocol`, the UDP transport used by twisted's DNS client (`twisted.names.client.Resolver`, `createResolver`, and anything built on it, including MX lookups in `twisted.mail`), accepts a DNS response for a pending query solely on the basis of the 16-bit transaction ID matching. It never checks that the response actually originated from the server the query was sent to. Any host that can deliver a UDP packet to the resolver's listening port with the correct transaction ID can inject a forged answer, independent of the real server's address. This is a materially weaker defense than standard DNS resolver practice (transaction ID plus source-address validation, typically also source-port rotation), and enables off-path DNS response spoofing / cache poisoning.

Details `DNSDatagramProtocol.datagramReceived` (`src/twisted/names/dns.py`, line 3350) is: ```python def datagramReceived(self, data, addr): """ Read a datagram, extract the message in…

Published by the source

27 Oct 2026, 14:45 UTC

Last modified by the source

27 Oct 2026, 15:00 UTC

Source last checked

28 Oct 2026, 06:20 UTC

1. Revision 2 · amended · 28 Oct 2026

   Amended from osv record GHSA-jj36-9pvh-vj5r

2. Revision 1 · created · 27 Oct 2026

   Published from ghsa record GHSA-jj36-9pvh-vj5r

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# Patch Next advisory brief: CVE-2026-83813

Advisory: Twisted: DNS Response Spoofing in twisted.names Due to Missing Source Address Validation
IDs: CVE-2026-83813, GHSA-jj36-9pvh-vj5r
Record: https://patchnext.com/advisories/cve-2026-83813 (revision 2, source checked 28 Oct 2026, 06:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: twisted 26.10.0rc1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI twisted: affected < 26.10.0rc1; fixed in 26.10.0rc1

## Suggested inspection (read-only)
- `python -m pip show twisted`: 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 twisted.
- 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-jj36-9pvh-vj5r (OSV record GHSA-jj36-9pvh-vj5r lists affected ranges: PyPI twisted >=0 <26.10.0rc1 (fixed))
- Verified: https://github.com/advisories/GHSA-jj36-9pvh-vj5r (GitHub-reviewed advisory GHSA-jj36-9pvh-vj5r lists affected ranges: PyPI twisted >=0 <=26.4.0)

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