Urwid: handle_short_request() crashes on non-ASCII POST body (UnicodeEncodeError DoS)

Exploitation

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

CVSS

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

EPSS

• CVE-2026-103022: 0.47% estimated exploitation activity in the next 30 days; percentile 41.15 (FIRST EPSS, 2026-11-10). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The `handle_short_request()` function in `urwid/display/web.py` raises an unhandled `UnicodeEncodeError` when processing a POST request body containing non-ASCII bytes. The function reads POST input and encodes it to ASCII before writing to a named pipe. Any byte value above `0x7F` causes the CGI process to exit with an unhandled exception, returning an HTTP 500 error to the client. Additionally, a file descriptor opened earlier in the same function is not closed before the exception propagates, causing a file descriptor leak for the lifetime of the CGI process. A second instance of missing exception handling exists in the polling update path, where non-UTF-8 socket output causes an unhandled `UnicodeDecodeError`.

Impact An attacker who observes a valid `X-Urwid-ID` session token (transmitted in plaintext HTTP response headers) can send repeated POST requests containing non-ASCII bytes to the `urwid` CGI endpoint. Each malformed request causes the CGI handler to crash…

Published by the source

9 Nov 2026, 22:05 UTC

Last modified by the source

9 Nov 2026, 22:15 UTC

Source last checked

10 Nov 2026, 06:35 UTC

1. Revision 2 · amended · 10 Nov 2026

   Amended from osv record GHSA-cp25-j9x5-p5xm

2. Revision 1 · created · 9 Nov 2026

   Published from ghsa record GHSA-cp25-j9x5-p5xm

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# Patch Next advisory brief: CVE-2026-103022

Advisory: Urwid: handle_short_request() crashes on non-ASCII POST body (UnicodeEncodeError DoS)
IDs: CVE-2026-103022, GHSA-cp25-j9x5-p5xm
Record: https://patchnext.com/advisories/cve-2026-103022 (revision 2, source checked 10 Nov 2026, 06:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: urwid 4.0.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI urwid: affected < 4.0.7; fixed in 4.0.7

## Suggested inspection (read-only)
- `python -m pip show urwid`: 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 urwid.
- 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-cp25-j9x5-p5xm (GitHub-reviewed advisory GHSA-cp25-j9x5-p5xm lists affected ranges: PyPI urwid >=0 <=4.0.6)
- Verified: https://osv.dev/vulnerability/GHSA-cp25-j9x5-p5xm (OSV record GHSA-cp25-j9x5-p5xm lists affected ranges: PyPI urwid >=0 <4.0.7 (fixed))

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