CVE-2026-49826

Concourse login flow has an open redirect issue

CVSS 4.0 0.0 NONEeuvd · severity unknownCVSS 4.0 · [email protected] · Secondary 0.0 NONECVSS_V4 Publisher rating LOWFixed by github.com/concourse/concourse 1.6.1-0.20260526150512-ac60be5f0435osv · severity unknownFixed by github.com/concourse/concourse 1.6.1-0.20260526150512-ac60be5f0435KEV status unknown

Original advisory

cve-program · CVE-2026-49826

Published

Concourse is a container-based automation system written in Go. Prior to version 8.2.3, an attacker is able to craft and send a user a URL that will redirect the user from the Concourse web server to any other site. This could be used in a phishing attack to steal user's credentials. This has been fixed in 8.2.3. No known workarounds are available.

Read the publisher's advisory

euvd · EUVD-2026-58716

Published

Read the publisher's advisory

nvd · CVE-2026-49826

Published

Read the publisher's advisory

osv · GHSA-8w27-c4vc-88q9

Published

### Impact An attacker is able to craft and send a user a URL that will redirect the user from the Concourse web server to any other site. This could be used in a phishing attack to steal user's credentials. ### Patches This has been fixed in 8.2.3 ### Workarounds None. ### Exploit Vulnerable code was in: https://github.com/concourse/concourse/blob/ea7b812e3a88fdd070f0faece874e8a2d4fbb31c/skymarshal/skyserver/skyserver.go#L162-L170 The issue stems from the underlying processing logic of Go's `url` package. Normally, `ParseRequestURI()` will eventually reach an internal `url.setPath()` function, where the URL will be decoded. However, if `RawPath` is not empty and `validEncoded(RawPath)` is true, and the decoded result equals `Path`, then return `RawPath` as is; otherwise, escape `Path` again, i.e., decode it again. In other words, if the URL contains dangerous characters that should be escaped, such as backslashes (`\`), then an extra decoding step will be performed. Therefore, `/%2Fexample.com` will be parsed as `//example.com`. On vulnerable versions of Concourse, add `/sky/login?redirect_uri=/%252Fexample.com/\` to your Concourse external URL, login as usual, and you should be redirected to `example.com` instead of your Concourse web server. The redirect happens after the login flow completes. No credentials are leaked.

Read the publisher's advisory

osv · GO-2026-5866

Published

Concourse login flow has an open redirect issue in github.com/concourse/concourse

Read the publisher's advisory

Affected versions, risk and source history

Exploitation and risk

Source status

CISA KEV lists vulnerabilities known to be exploited. FIRST EPSS estimates the likelihood of exploitation in the next 30 days. An unavailable score does not mean zero risk.

Which CVEs have scores here?

This view includes predictions for CVE identifiers explicitly listed in public NuGet advisories. Microsoft release pages have their own prediction coverage. Check source status for the scope and latest checks.

No exploitation or prediction data is available here for these CVEs. This does not mean they are safe or unlikely to be exploited.

Risk history

Compare earlier KEV listings and daily EPSS scores. Advisory wording and affected versions have a separate history.

When does an EPSS score appear as a change?

A prediction change is reported when EPSS rises from below 10% to 10% or higher. Other daily score changes remain in this history.

Advisory history

12 saved versions

See how the publisher's advisory changed over time. Each link opens the version saved at that time. The publisher's update date can differ from the date shown here.

How advisory history works

Each link identifies one complete publisher record. History can include advisories that previously shared an identifier; an identifier removed by a publisher no longer establishes a current relationship. A historical link shows only that record and earlier saved versions. Failed checks and unchanged reads do not create new versions.

11 Nov 2026 14:09:31 UTC