python-socketio: Binary attachment accumulation can cause denial of service

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-2026-48804: 0.49% estimated exploitation activity in the next 30 days; percentile 42.05 (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.

Impact The python-socketio server stores binary EVENT and ACK messages in memory while it waits to receive their binary attachments. Once all the attachments are received, these messages are then processed. An attacker can submit a binary message and intentionally omit sending one or more of its attachments to cause the message along with the partial list of received attachments to stay in memory for a long time. Patches Version 5.16.2 takes the following measures to address this issue: - Binary packets are only accepted from authenticated clients. - When a client disconnects, the server checks if there is a partial binary message being held for the client and deletes it.

Published by the source

26 Jun 2026, 20:51 UTC

Last modified by the source

13 Jul 2026, 16:43 UTC

Source last checked

26 Oct 2026, 13:46 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-5w7q-77mv-v69f

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-5w7q-77mv-v69f

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# Patch Next advisory brief: CVE-2026-48804

Advisory: python-socketio: Binary attachment accumulation can cause denial of service
IDs: CVE-2026-48804, GHSA-5w7q-77mv-v69f
Record: https://patchnext.com/advisories/cve-2026-48804 (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: python-socketio 5.16.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI python-socketio: affected <= 5.16.1; fixed in 5.16.2

## Suggested inspection (read-only)
- `python -m pip show python-socketio`: 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 python-socketio.
- 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-5w7q-77mv-v69f (OSV record GHSA-5w7q-77mv-v69f lists affected ranges: PyPI python-socketio >=0 <5.16.2 (fixed))
- Verified: https://github.com/advisories/GHSA-5w7q-77mv-v69f (GitHub-reviewed advisory GHSA-5w7q-77mv-v69f lists affected ranges: PyPI python-socketio >=0 <=5.16.1)

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