Vulnerability · Published Aug 20, 2026 · Assigned by GitHub_M
CVE-2026-54770WebOb: Open redirect in Location header normalization via leading C0 control / space characters
Medium 6.1
In plain English
A medium-severity open redirect in webob from Pylons. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 37% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
WebOb provides objects for HTTP requests and responses. Prior to 1.8.11, Response._make_location_absolute() in src/webob/response.py checks a Location value for a URI scheme or leading double slash before urllib.parse.urljoin() strips leading C0 control characters and spaces. An attacker-controlled value such as a space followed by a protocol-relative or absolute URL can therefore bypass SCHEME_RE and startswith("//") checks and be normalized to an off-host redirect. Request.relative_url() and webob.exc._HTTPMove subclasses, including HTTPFound, are also affected because they use the same unsafe URL joining behavior or bypass the earlier normalization path. An unauthenticated attacker who can influence an application's redirect target can send users to an attacker-controlled host for phishing or OAuth and SSO token theft, but exploitation requires the user to follow the redirect. This issue is fixed in version 1.8.11.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | python-webob | no fix listed | DEBIAN-CVE-2026-54770 |
| Debian:13 | python-webob | no fix listed | DEBIAN-CVE-2026-54770 |
| Debian:14 | python-webob | 1:1.8.11-1 | DEBIAN-CVE-2026-54770 |
| PyPI | webob | 1.8.11 | GHSA-6hx8-3wjj-gr8g |
| PyPI | webob | 1.8.11 | PYSEC-2026-3943 |
| Ubuntu:22.04:LTS | python-webob | no fix listed | UBUNTU-CVE-2026-54770 |
| Ubuntu:24.04:LTS | python-webob | no fix listed | UBUNTU-CVE-2026-54770 |
| Ubuntu:26.04:LTS | python-webob | no fix listed | UBUNTU-CVE-2026-54770 |
| Ubuntu:26.10 | python-webob | no fix listed | UBUNTU-CVE-2026-54770 |
Affected products (as reported)
Weakness: CWE-601 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
References
- https://github.com/Pylons/webob/security/advisories/GHSA-6hx8-3wjj-gr8g x_refsource_CONFIRM
- https://github.com/Pylons/webob/commit/ff89560643fb252751b4db8806a283b5377f1f07 x_refsource_MISC
- https://github.com/Pylons/webob/tree/1.8.11 x_refsource_MISC