CVE-2026-44889 WebOb: Location header normalization during redirect leads to open redirect

What is CVE-2026-44889?

CVE-2026-44889 is a medium-severity vulnerability in Pylons webob, published on 22 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

WebOb provides objects for HTTP requests and responses. Prior to 1.8.10, the normalization of the HTTP Location header during a redirect is vulnerable to an open redirect: WebOb joins the redirect target to the request URI using Python's urljoin, and since Python 3.10 the underlying urlsplit strips ASCII tab, carriage return, and newline characters before parsing, so a redirect target containing such characters can be reinterpreted as a protocol-relative URL whose authority is an attacker-controlled host. This bypasses the CVE-2024-42353 fix that escaped a leading double slash, allowing an attacker who influences the redirect location to send users to an arbitrary external site instead of the intended one. This vulnerability is fixed in 1.8.10.

Weakness: CWE-601

Which versions are affected by CVE-2026-44889?

3 open source packages ship an affected version, including webob. It affects 1 product.

Products include Pylonsproject Webob.

How do I fix CVE-2026-44889?

Upgrade webob to 1.8.10 or later.

Is CVE-2026-44889 being exploited?

There is no known exploitation of CVE-2026-44889 in the wild and no public exploit code.

Other vulnerabilities in Pylons webob

• CVE-2024-42353 WebOb's location header normalization during redirect leads to open redirect Medium 6.1

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-91362, DEBIAN-CVE-2026-44889, ECHO-0b2f-27c4-24aa, GHSA-fh3h-vg37-cc95, MGASA-2026-0452, OESA-2026-2679 and 6 more.