CVE-2026-54770: WebOb: Open redirect in Location header normalization via leading C0 control / space characters

mediumCVSS 6.1CVE-2026-54770

CSIRTS triage

vendor: WebOb product: WebOb Cross-site scripting

What: WebOb's Location header normalization is bypassable via leading C0 control or space characters, enabling open redirects.
Who is affected: WebOb-based applications using Location header normalization for redirect validation.
Urgency: Medium; open redirect risk in authentication or external link handling.
Action: Upgrade WebOb to the patched version and test redirect validation logic.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 6.1
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54770

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-547700.34% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 26% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-54770	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

mediumCVE-2026-54770: WebOb provides objects for HTTP requests and responses. Prior to 1.8.11, Response._make_locati…nvd

Recent advisories for WebOb

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

mediumCVE-2026-54770: WebOb provides objects for HTTP requests and responses. Prior to 1.8.11, Response._make_locati…nvd · 2026-08-20
mediumCVE-2026-44889: WebOb: Location header normalization during redirect leads to open redirectmsrc · 2026-06-09
mediumGHSA-fh3h-vg37-cc95: WebOb: Location header normalization during redirect leads to open redirect - againghsa · 2026-06-04